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Estonian Basic-School Physics Exam study materials
Estonian Basic-School Physics Exam study resources

Estonian Basic-School Physics Exam practice questions

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Question 1Kinematics and mechanics (motion, forces, pressure, work and energy)

A cyclist rides 300 m east in 20 s, then 100 m east in 10 s. What is the cyclist's average speed for the whole trip?

  1. 13.3 m/s Correct answer.
  2. 10.0 m/s
  3. 20.0 m/s
  4. 15.0 m/s

Explanation

Average speed equals total distance divided by total time. The total distance is 300 m + 100 m = 400 m and the total time is 20 s + 10 s = 30 s, so the average speed is 400/30 ≈ 13.3 m/s. Adding the two separate speeds and halving them gives a wrong result because the time intervals differ.

Question 2Kinematics and mechanics (motion, forces, pressure, work and energy)

Which of these is a vector quantity?

  1. Temperature
  2. Force Correct answer.
  3. Mass
  4. Time

Explanation

A vector has both magnitude and direction. Force is described by how large it is and which way it points, so it is a vector. Mass, time and temperature have magnitude only and are scalars.

Question 3Kinematics and mechanics (motion, forces, pressure, work and energy)

A book rests on a horizontal table. Which statement about the forces on the book is correct?

  1. The normal force points downward, in the same direction as the weight.
  2. There is no normal force because the book is not moving.
  3. The normal force from the table balances the book's weight, so the net force is zero. Correct answer.
  4. The book's weight is greater than the normal force, so the book slowly sinks.

Explanation

Because the book is at rest, the net force on it must be zero. The upward normal force from the table therefore has the same magnitude as the downward weight. The two forces act in opposite directions and cancel.

Question 4Kinematics and mechanics (motion, forces, pressure, work and energy)

A stone is dropped from rest and falls freely for 3 s. Taking g = 10 m/s², what is its speed just before it lands?

  1. 45 m/s
  2. 3 m/s
  3. 30 m/s Correct answer.
  4. 10 m/s

Explanation

For free fall from rest, speed equals g times the time of fall. With g = 10 m/s² and t = 3 s, the speed is 10 × 3 = 30 m/s. The value 45 m is the distance fallen, not the speed.

Question 5Kinematics and mechanics (motion, forces, pressure, work and energy)

What is the SI unit of pressure?

  1. The watt
  2. The pascal Correct answer.
  3. The joule
  4. The newton

Explanation

Pressure is force per unit area, so its unit is the newton per square metre, called the pascal (Pa). The newton measures force, the joule measures energy and the watt measures power.

Question 6Kinematics and mechanics (motion, forces, pressure, work and energy)

Which form of energy is stored in a stretched rubber band?

  1. Chemical energy
  2. Kinetic energy
  3. Thermal energy
  4. Elastic potential energy Correct answer.

Explanation

A stretched or compressed object stores elastic potential energy because of its changed shape. This energy is released when the object returns to its original shape. Kinetic energy belongs to moving objects, not to a stretched band held at rest.

Question 7Kinematics and mechanics (motion, forces, pressure, work and energy)

A box is pushed with a constant horizontal force of 20 N and moves 5 m in the direction of the force. How much work is done by this force?

  1. 4 J
  2. 25 J
  3. 100 J Correct answer.
  4. 0 J

Explanation

Work equals force times the distance moved in the direction of the force. Here W = 20 N × 5 m = 100 J. Dividing force by distance instead of multiplying gives an incorrect value.

Question 8Kinematics and mechanics (motion, forces, pressure, work and energy)

A car travels at a steady 15 m/s along a straight road. What distance does it cover in 8 s?

  1. 60 m
  2. 1.9 m
  3. 120 m Correct answer.
  4. 23 m

Explanation

For constant speed, distance equals speed multiplied by time. Here d = 15 m/s × 8 s = 120 m. The other values come from adding, dividing or halving the given numbers incorrectly.

Question 9Kinematics and mechanics (motion, forces, pressure, work and energy)

A car accelerates uniformly from 5 m/s to 25 m/s in 10 s. What is its acceleration?

  1. 0.5 m/s²
  2. 2 m/s² Correct answer.
  3. 20 m/s²
  4. 3 m/s²

Explanation

Acceleration is the change in velocity divided by the time taken. The change is 25 − 5 = 20 m/s, and dividing by 10 s gives 2 m/s². Using the final velocity alone or the time alone gives wrong results.

Question 10Kinematics and mechanics (motion, forces, pressure, work and energy)

A 2 kg object is pushed across a frictionless surface by a net force of 6 N. What is its acceleration?

  1. 12 m/s²
  2. 3 m/s² Correct answer.
  3. 0.33 m/s²
  4. 8 m/s²

Explanation

Newton's second law states that acceleration equals net force divided by mass. Here a = 6 N / 2 kg = 3 m/s². Multiplying the force by the mass or adding them does not give acceleration.

Question 11Kinematics and mechanics (motion, forces, pressure, work and energy)

Two forces act on a point: 8 N to the right and 3 N to the left, along the same line. What is the magnitude of the resultant force and its direction?

  1. 24 N to the right
  2. 5 N to the right Correct answer.
  3. 11 N to the right
  4. 5 N to the left

Explanation

Forces along the same line combine by subtracting opposing magnitudes. The larger force is 8 N to the right, so the resultant is 8 − 3 = 5 N to the right. Adding the magnitudes would only be correct if both forces pointed the same way.

Question 12Kinematics and mechanics (motion, forces, pressure, work and energy)

A block of weight 40 N rests on a horizontal surface. The contact area between block and surface is 0.2 m². What pressure does the block exert on the surface?

  1. 0.005 Pa
  2. 40 Pa
  3. 200 Pa Correct answer.
  4. 8 Pa

Explanation

Pressure equals force divided by area. Here p = 40 N / 0.2 m² = 200 Pa. Multiplying force by area or dividing area by force gives incorrect values.

Question 13Kinematics and mechanics (motion, forces, pressure, work and energy)

A 0.5 kg ball is lifted to a height of 4 m above the ground. Taking g = 10 m/s², what is its gravitational potential energy relative to the ground?

  1. 200 J
  2. 2 J
  3. 20 J Correct answer.
  4. 0 J

Explanation

Gravitational potential energy equals mgh. Here it is 0.5 kg × 10 m/s² × 4 m = 20 J. The value depends on height, so it is not zero at 4 m above the reference level.

Question 14Kinematics and mechanics (motion, forces, pressure, work and energy)

A machine does 600 J of useful work in 4 s. What is its useful power output?

  1. 150 W Correct answer.
  2. 600 W
  3. 0.0067 W
  4. 2400 W

Explanation

Power is work done divided by the time taken. Here P = 600 J / 4 s = 150 W. Multiplying work by time or dividing time by work does not give power.

Question 15Kinematics and mechanics (motion, forces, pressure, work and energy)

A car of mass 1000 kg moves at 20 m/s. What is its kinetic energy?

  1. 20 000 J
  2. 400 000 J
  3. 10 000 J
  4. 200 000 J Correct answer.

Explanation

Kinetic energy equals ½mv². Here it is ½ × 1000 kg × (20 m/s)² = ½ × 1000 × 400 = 200 000 J. Forgetting to square the speed or omitting the factor of ½ gives the other values.

Question 16Kinematics and mechanics (motion, forces, pressure, work and energy)

A skydiver falls at a constant terminal velocity. Which statement describes the forces on the skydiver at that moment?

  1. There is no air resistance once terminal velocity is reached.
  2. Air resistance is greater than the weight, so the skydiver slows down.
  3. Air resistance equals the weight, so the net force is zero. Correct answer.
  4. Air resistance is less than the weight, so the skydiver keeps accelerating.

Explanation

Constant velocity means zero net force by Newton's first law. The upward air resistance therefore balances the downward weight exactly. If either force were larger, the velocity would change.

Question 17Kinematics and mechanics (motion, forces, pressure, work and energy)

A lever is used to lift a load. The effort arm is 1.2 m and the load arm is 0.3 m. Ignoring friction, what effort is needed to lift a load of 200 N?

  1. 800 N
  2. 200 N
  3. 240 N
  4. 50 N Correct answer.

Explanation

For a lever in equilibrium, effort × effort arm = load × load arm. So effort = (200 N × 0.3 m) / 1.2 m = 50 N. The longer effort arm gives a mechanical advantage, so the effort is smaller than the load.

Question 18Kinematics and mechanics (motion, forces, pressure, work and energy)

A cube of side 0.1 m floats in water with half its volume submerged. Taking the density of water as 1000 kg/m³, what is the buoyant force on the cube?

  1. 50 N
  2. 10 N
  3. 5 N Correct answer.
  4. 0.5 N

Explanation

The cube's volume is 0.1³ = 0.001 m³, and half of it is submerged, so 0.0005 m³ is displaced. The buoyant force equals the weight of displaced water: 1000 × 0.0005 × 10 = 5 N. Using the full volume or the wrong side length gives the other values.

Question 19Kinematics and mechanics (motion, forces, pressure, work and energy)

A person walks 4 m north, then 3 m east. What is the magnitude of the displacement from the starting point?

  1. 1 m
  2. 5 m Correct answer.
  3. 7 m
  4. 12 m

Explanation

The two displacements are perpendicular, so they form the legs of a right triangle. The displacement magnitude is the hypotenuse: √(4² + 3²) = √25 = 5 m. Simply adding the distances ignores the change in direction.

Question 20Kinematics and mechanics (motion, forces, pressure, work and energy)

An object moves along a straight line with constant acceleration. Its velocity–time graph is a straight line rising from 2 m/s at t = 0 to 10 m/s at t = 4 s. What distance does it travel in these 4 s?

  1. 40 m
  2. 32 m
  3. 24 m Correct answer.
  4. 8 m

Explanation

The distance is the area under the velocity–time graph. The area is a trapezium: ½ × (2 + 10) × 4 = 24 m. Using only the final velocity or only the change in velocity gives the other values.

Question 21Kinematics and mechanics (motion, forces, pressure, work and energy)

A 5 kg crate slides along a rough floor. The friction force is 15 N and the crate slides 4 m before stopping. How much energy is dissipated by friction?

  1. 20 J
  2. 60 J Correct answer.
  3. 3.75 J
  4. 75 J

Explanation

The energy dissipated by friction equals the friction force times the distance slid. Here it is 15 N × 4 m = 60 J. This energy leaves the crate's kinetic energy and becomes thermal energy in the surfaces.

Question 22Kinematics and mechanics (motion, forces, pressure, work and energy)

Two objects collide on a frictionless surface and stick together. Which quantity is conserved during the collision?

  1. Total kinetic energy
  2. Total speed of each object
  3. Total force on each object
  4. Total momentum Correct answer.

Explanation

In the absence of external forces, total momentum is conserved in a collision. Kinetic energy is not conserved when the objects stick together because the collision is inelastic. Individual speeds and forces change during the impact.

Question 23Kinematics and mechanics (motion, forces, pressure, work and energy)

A ball is thrown vertically upward with an initial speed of 20 m/s. Taking g = 10 m/s² and ignoring air resistance, what is the maximum height reached?

  1. 2 m
  2. 10 m
  3. 40 m
  4. 20 m Correct answer.

Explanation

At the highest point the speed is zero, so the initial kinetic energy becomes potential energy: ½v² = gh. Thus h = v²/(2g) = 400/20 = 20 m. Using v²/g without the factor of 2 doubles the height.

Question 24Kinematics and mechanics (motion, forces, pressure, work and energy)

A hydraulic press has a small piston of area 0.01 m² and a large piston of area 0.5 m². A force of 100 N is applied to the small piston. What force is produced on the large piston?

  1. 5000 N Correct answer.
  2. 2 N
  3. 2000 N
  4. 100 N

Explanation

Pascal's principle states that pressure is transmitted equally through a confined fluid. The pressure is 100 N / 0.01 m² = 10 000 Pa, so the force on the large piston is 10 000 Pa × 0.5 m² = 5000 N. The area ratio of 50 multiplies the applied force.

Question 25Kinematics and mechanics (motion, forces, pressure, work and energy)

A crane lifts a 200 kg load at a constant speed of 0.5 m/s. Taking g = 10 m/s², what power does the crane deliver to the load?

  1. 100 W
  2. 2000 W
  3. 4000 W
  4. 1000 W Correct answer.

Explanation

Power equals force times speed when the force acts along the motion. The lifting force equals the weight, 200 × 10 = 2000 N, so P = 2000 N × 0.5 m/s = 1000 W. Using the mass instead of the weight gives a wrong result.

Question 26Kinematics and mechanics (motion, forces, pressure, work and energy)

A cyclist rides 300 m east in 20 s and then 300 m west in 30 s. What is the average speed for the whole journey?

  1. 10 m/s
  2. 6 m/s
  3. 12 m/s Correct answer.
  4. 0 m/s

Explanation

Average speed uses total distance divided by total time: 600 m ÷ 50 s = 12 m/s. Distance travelled is always positive, so the opposite directions do not cancel. Only average velocity would use displacement, which here is zero.

Question 27Kinematics and mechanics (motion, forces, pressure, work and energy)

A stone is dropped from rest and falls freely for 3 s. Taking g = 10 m/s² and ignoring air resistance, how far does it fall?

  1. 15 m
  2. 90 m
  3. 45 m Correct answer.
  4. 30 m

Explanation

For motion from rest, distance = ½gt² = ½ × 10 × 3² = 45 m. The factor ½ appears because the speed grows steadily from zero, so the average speed is half the final speed. Multiplying g by t alone gives speed, not distance.

Question 28Kinematics and mechanics (motion, forces, pressure, work and energy)

A force of 12 N acts on a body and produces an acceleration of 3 m/s². What is the mass of the body?

  1. 4 kg Correct answer.
  2. 9 kg
  3. 36 kg
  4. 0.25 kg

Explanation

Newton's second law gives m = F/a = 12 N ÷ 3 m/s² = 4 kg. Acceleration is inversely proportional to mass for a fixed force. Multiplying force by acceleration is not a valid operation here.

Question 29Kinematics and mechanics (motion, forces, pressure, work and energy)

A book rests on a horizontal table. Which pair of forces forms an action–reaction pair according to Newton's third law?

  1. The friction on the book and the normal force on the book
  2. The book's weight and the gravitational pull of the book on the Earth Correct answer.
  3. The normal force on the book and the weight of the table
  4. The book's weight and the normal force from the table on the book

Explanation

Action–reaction pairs act on two different bodies, are equal in size, opposite in direction and of the same type. The Earth pulls the book down, and the book pulls the Earth up with an equal gravitational force. The weight and normal force both act on the book, so they are balanced forces rather than a third-law pair.

Question 30Kinematics and mechanics (motion, forces, pressure, work and energy)

A crate is dragged across a rough floor at constant velocity by a horizontal force of 50 N. What is the magnitude of the friction force acting on the crate?

  1. Less than 50 N
  2. 0 N
  3. More than 50 N
  4. 50 N Correct answer.

Explanation

Constant velocity means zero acceleration, so the net horizontal force must be zero. The pulling force and friction therefore have equal magnitudes, 50 N. Friction is not absent just because the crate is moving.

Question 31Kinematics and mechanics (motion, forces, pressure, work and energy)

A uniform metre rule is balanced at its centre. A 2 N weight hangs 20 cm to the left of the pivot. Where must a 4 N weight be hung to keep the rule horizontal?

  1. 5 cm to the right of the pivot
  2. 20 cm to the right of the pivot
  3. 40 cm to the right of the pivot
  4. 10 cm to the right of the pivot Correct answer.

Explanation

For balance, the moments about the pivot must be equal: 2 N × 20 cm = 40 N·cm. The 4 N weight must therefore act at 40 ÷ 4 = 10 cm from the pivot on the opposite side. A larger force needs a shorter lever arm to give the same moment.

Question 32Kinematics and mechanics (motion, forces, pressure, work and energy)

Which statement correctly describes the pressure at a point inside a liquid at rest?

  1. It depends only on the shape of the container.
  2. It acts only downwards, like the weight of the liquid.
  3. It increases with depth and acts equally in all directions. Correct answer.
  4. It is the same at all depths regardless of depth.

Explanation

Pressure in a liquid at rest equals ρgh, so it grows with depth and depends on the liquid's density. At any point it pushes equally in every direction, which is why a hole in a container lets water out sideways as well as downwards. The shape of the container does not change the pressure at a given depth.

Question 33Kinematics and mechanics (motion, forces, pressure, work and energy)

A solid metal block sinks when placed in water. Which comparison explains this?

  1. The block has no upthrust acting on it in water.
  2. The weight of the block is less than the upthrust on it.
  3. The volume of the block is greater than the volume of water.
  4. The density of the metal is greater than the density of water. Correct answer.

Explanation

An object sinks when its weight exceeds the upthrust, which for a fully submerged body happens when its density is greater than the liquid's. Archimedes' principle still gives an upthrust on a sinking block; it is simply too small to balance the weight. Comparing volumes alone does not decide floating or sinking.

Question 34Kinematics and mechanics (motion, forces, pressure, work and energy)

A spring stretches by 4 cm when a 2 N load hangs from it, staying within its elastic limit. What load will stretch the same spring by 10 cm?

  1. 8 N
  2. 20 N
  3. 5 N Correct answer.
  4. 2.5 N

Explanation

Hooke's law states that extension is proportional to the applied force. The extension grows from 4 cm to 10 cm, a factor of 2.5, so the force becomes 2 N × 2.5 = 5 N. The spring constant here is 2 N ÷ 0.04 m = 50 N/m.

Question 35Kinematics and mechanics (motion, forces, pressure, work and energy)

A ball is kicked and rolls along a level floor, gradually slowing down. Which statement best explains why it stops?

  1. The ball's inertia decreases as it slows.
  2. The ball's forward force gradually runs out.
  3. Gravity pulls the ball backwards along the floor.
  4. Friction and air resistance exert a backward force on the ball. Correct answer.

Explanation

A net force is needed to change motion, and here friction and air resistance act opposite to the motion, giving a backward net force that decelerates the ball. No forward force is needed to keep it moving; the ball simply loses speed. Inertia is a fixed property of the ball's mass and does not run down.

Question 36Kinematics and mechanics (motion, forces, pressure, work and energy)

A car of mass 800 kg travelling at 10 m/s brakes and stops in 4 s. What is the magnitude of the average braking force?

  1. 320 N
  2. 800 N
  3. 8000 N
  4. 2000 N Correct answer.

Explanation

The deceleration is (10 − 0) ÷ 4 = 2.5 m/s². Using F = ma gives 800 kg × 2.5 m/s² = 2000 N. Alternatively, the change in momentum is 8000 kg·m/s, and dividing by 4 s gives the same force.

Question 37Kinematics and mechanics (motion, forces, pressure, work and energy)

An object moves in a straight line at constant speed. Which statement about the forces on it is necessarily true?

  1. No forces at all act on it.
  2. The net force on it is zero. Correct answer.
  3. The forward force is larger than any backward force.
  4. A single forward force acts on it.

Explanation

Constant velocity means zero acceleration, so by Newton's first law the resultant force must be zero. Individual forces may still act, as long as they cancel. It is not necessary for the object to be free of forces.

Question 38Kinematics and mechanics (motion, forces, pressure, work and energy)

A worker pushes a crate with a horizontal force of 100 N, but the crate does not move. How much work does the pushing force do on the crate?

  1. 0 J Correct answer.
  2. More than 100 J
  3. It depends on the mass of the crate
  4. 100 J

Explanation

Work equals force multiplied by displacement in the direction of the force. If the crate does not move, the displacement is zero, so no work is done by the push. Effort alone does not guarantee energy transfer to the crate.

Question 39Kinematics and mechanics (motion, forces, pressure, work and energy)

A pump raises 60 kg of water through a height of 5 m every minute. Taking g = 10 m/s², what is the useful power of the pump?

  1. 3000 W
  2. 600 W
  3. 50 W Correct answer.
  4. 300 W

Explanation

The work done against gravity is mgh = 60 × 10 × 5 = 3000 J. Power is work divided by time, so 3000 J ÷ 60 s = 50 W. Dividing by the full minute is essential because power is a rate.

Question 40Kinematics and mechanics (motion, forces, pressure, work and energy)

A ball rolls down a frictionless slope from a height of 1.8 m. Taking g = 10 m/s², what is its speed at the bottom?

  1. 18 m/s
  2. 3 m/s
  3. 6 m/s Correct answer.
  4. 36 m/s

Explanation

With no friction, gravitational potential energy converts entirely to kinetic energy: gh = ½v². So v = √(2 × 10 × 1.8) = √36 = 6 m/s. The result is independent of the ball's mass.

Question 41Kinematics and mechanics (motion, forces, pressure, work and energy)

A machine is supplied with 500 J of energy and delivers 350 J of useful work. What is its efficiency?

  1. 70 % Correct answer.
  2. 30 %
  3. 35 %
  4. 150 %

Explanation

Efficiency is useful output divided by total input, expressed as a percentage: 350 ÷ 500 = 0.70, or 70 %. The remaining 150 J is wasted, mainly as heat and sound. Efficiency can never exceed 100 %.

Question 42Kinematics and mechanics (motion, forces, pressure, work and energy)

A car travels along a straight road. Its velocity–time graph is a horizontal line above the time axis. What does the area under the graph between two times represent?

  1. The force on the car
  2. The mass of the car
  3. The acceleration of the car
  4. The distance travelled by the car Correct answer.

Explanation

On a velocity–time graph, the area under the line equals velocity × time, which is displacement, here equal to distance because motion is in one direction. The gradient of the line would give acceleration instead. A horizontal line means constant velocity, so acceleration is zero.

Question 43Kinematics and mechanics (motion, forces, pressure, work and energy)

A sprinter starts from rest and accelerates uniformly at 2 m/s² for 5 s. What distance does she cover in this time?

  1. 25 m Correct answer.
  2. 50 m
  3. 10 m
  4. 20 m

Explanation

Using s = ½at² from rest: ½ × 2 × 5² = 25 m. Her final speed is 10 m/s, and the average speed over the interval is 5 m/s, which multiplied by 5 s also gives 25 m. Multiplying acceleration by time alone gives speed, not distance.

Question 44Kinematics and mechanics (motion, forces, pressure, work and energy)

A box sits on a rough horizontal floor. The pushing force is gradually increased until the box just begins to slide. Which statement describes what happens at that instant?

  1. The normal force disappears once the box moves.
  2. Kinetic friction is always larger than the maximum static friction.
  3. Static friction becomes zero as the box starts to move.
  4. Static friction reaches its maximum value and is then replaced by sliding friction. Correct answer.

Explanation

Static friction grows to match the applied force until it reaches a maximum, after which the surfaces slip. Once sliding begins, kinetic friction acts and is usually slightly smaller than the maximum static value. The normal force does not vanish; it remains equal to the weight on a horizontal floor.

Question 45Kinematics and mechanics (motion, forces, pressure, work and energy)

Two children sit on a seesaw that is balanced. Child A has mass 30 kg and sits 1.2 m from the pivot. How far from the pivot must child B, of mass 40 kg, sit?

  1. 0.6 m
  2. 0.9 m Correct answer.
  3. 1.6 m
  4. 1.2 m

Explanation

Balance requires equal moments: 30 × 1.2 = 36 kg·m. Child B must sit at 36 ÷ 40 = 0.9 m from the pivot. The heavier child sits closer to the pivot to produce the same turning effect.

Question 46Kinematics and mechanics (motion, forces, pressure, work and energy)

A diver swims deeper in a lake. Which quantities both increase as the depth increases?

  1. Pressure on the diver only, while upthrust stays the same Correct answer.
  2. Pressure on the diver and upthrust on the diver
  3. Upthrust on the diver only, while pressure stays the same
  4. Neither pressure nor upthrust changes with depth

Explanation

Pressure in a liquid increases with depth according to p = ρgh, so the diver feels a greater pressure. Upthrust depends on the volume of displaced liquid and its density, which do not change as the diver goes deeper, so upthrust stays the same. This distinction between depth-dependent pressure and volume-dependent upthrust is a common exam point.

Question 47Kinematics and mechanics (motion, forces, pressure, work and energy)

A force of 30 N pulls a sled 8 m along horizontal ground, and the force acts in the direction of motion. How much work is done by this force?

  1. 240 J Correct answer.
  2. 120 J
  3. 3.75 J
  4. 38 J

Explanation

When the force is along the displacement, work = F × s = 30 N × 8 m = 240 J. Work measures energy transferred by the force. Adding the values or dividing them has no physical meaning.

Question 48Kinematics and mechanics (motion, forces, pressure, work and energy)

An object is thrown horizontally from a table and lands on the floor. Ignoring air resistance, how do its horizontal and vertical motions compare?

  1. The vertical motion is uniform, while the horizontal motion is uniformly accelerated.
  2. Both horizontal and vertical motions are uniformly accelerated.
  3. The horizontal motion is uniform, while the vertical motion is uniformly accelerated. Correct answer.
  4. Both horizontal and vertical motions are uniform.

Explanation

Once released, no horizontal force acts (ignoring air resistance), so the horizontal velocity stays constant. Vertically, gravity provides a constant downward acceleration g, so the vertical speed grows steadily. The two components are independent, which is why the path is a parabola.

Question 49Kinematics and mechanics (motion, forces, pressure, work and energy)

A force of 10 N acts on a body and moves it 3 m in the direction of the force. The same force then acts on a second body and moves it 6 m. How does the work done on the second body compare with the first?

  1. It is twice as much. Correct answer.
  2. It is half as much.
  3. It is the same.
  4. It is four times as much.

Explanation

Work equals force times displacement in the direction of the force. With the same 10 N force, doubling the displacement from 3 m to 6 m doubles the work from 30 J to 60 J. Work is directly proportional to displacement for a constant force.

Question 50Kinematics and mechanics (motion, forces, pressure, work and energy)

A 1500 kg car accelerates uniformly from rest to 20 m/s over a distance of 100 m. What is the net force on the car?

  1. 1500 N
  2. 300 N
  3. 3000 N Correct answer.
  4. 600 N

Explanation

Using v² = 2as gives a = v² ÷ (2s) = 400 ÷ 200 = 2 m/s². Then F = ma = 1500 × 2 = 3000 N. Alternatively, the kinetic energy gained is 300 000 J, and dividing by the 100 m distance gives the same net force.