Maharashtra SSC Workshop Science & Calculation ITI flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Improper fraction

A fraction whose numerator is equal to or greater than its denominator, such as 7/4. Dividing gives a mixed number: 7/4 equals 1 whole and 3/4.

Percentage change

The difference between new and old value divided by the old value, multiplied by 100. A 10% rise followed by a 10% fall leaves 99, not the original 100.

Ratio comparison

To compare two ratios, express them as fractions or cross-multiply. For 3:4 and 5:7, cross products 21 and 20 show that 3:4 is the larger ratio.

Area of a circle

The area enclosed by a circle equals pi times the radius squared, or pi times diameter squared divided by four. With pi about 3.1416, a 50 mm diameter gives about 1963 mm squared.

Cylinder volume

Volume of a right cylinder equals base area times height, that is pi times radius squared times height. Curved surface area is 2 pi r h, excluding the two flat ends.

Cone slant height

The straight distance from apex to rim of the base, found by Pythagoras: square root of radius squared plus height squared. Curved surface area equals pi times radius times slant height.

Heron's formula

A way to find triangle area from three sides alone. Compute s as half the perimeter, then area equals the square root of s times (s minus a) times (s minus b) times (s minus c).

Tangent ratio

In a right triangle, tangent of an angle equals the opposite side divided by the adjacent side. It also equals sine divided by cosine and is used to find taper half-angles.

Sine and cosine rules

For any triangle, sides divided by the sines of opposite angles are equal. The cosine rule gives a side from two sides and the included angle: a squared equals b squared plus c squared minus 2bc cos A.

Angle of elevation

The angle measured upward from the horizontal line of sight to an object above. Together with a measured horizontal distance it gives height by the tangent ratio.

Density formula

Density equals mass divided by volume. Steel is about 7850 kilograms per cubic metre, so a one-litre steel part has a mass of roughly 7.85 kilograms.

Work and power

Work equals force times distance moved along the force, in joules. Power equals work divided by time, in watts, so one joule per second is one watt.

Mechanical advantage

Load divided by effort for a machine. Velocity ratio is effort distance divided by load distance, and efficiency is mechanical advantage divided by velocity ratio, expressed as a percentage.

Torque versus work

Torque is force times perpendicular radius, in newton metres. Unlike work, no displacement along the force occurs, so torque is not measured in joules despite identical units.

Cutting speed formula

Surface speed in metres per minute equals pi times diameter in millimetres times rpm divided by 1000. Rearranged, rpm equals 1000 times speed divided by pi times diameter.

Turning machining time

Time per pass equals length of cut divided by feed per revolution times rpm. Add approach and overtravel to the actual job length before dividing.

Milling table feed

Table feed in millimetres per minute equals feed per tooth times number of teeth times spindle rpm. It sets how fast the workpiece advances under the cutter.

Gear module

Module equals pitch circle diameter divided by number of teeth. Meshing gears need equal module and pressure angle, and centre distance is module times the sum of teeth divided by two.

Taper half-angle

The tangent of the half-angle equals big diameter minus small diameter, divided by twice the taper length. The included angle is twice this half-angle.

Tap drill size

For ISO metric threads, the tapping drill diameter is approximately the major diameter minus the pitch. An M10 with 1.5 mm pitch takes an 8.5 mm drill.

Clearance and interference fits

In a clearance fit the hole is always larger than the shaft, allowing movement. In an interference fit the shaft is always larger, so force or heat is needed for assembly.

Celsius to Fahrenheit

Multiply the Celsius reading by nine fifths and add 32. The reverse subtracts 32 first, then multiplies by five ninths. Kelvin equals Celsius plus 273.15.

Sensible heat formula

Heat absorbed or released equals mass times specific heat capacity times temperature change. Water needs about 4.18 kilojoules per kilogram for each kelvin rise.

Ohm's law and power

Voltage equals current times resistance. Power equals voltage times current, also current squared times resistance, or voltage squared divided by resistance.

Brass and bronze

Brass is an alloy of copper and zinc. Bronze is copper with tin. Bronze resists wear better and is preferred for bearings and bushes, while brass machines and casts easily.

Annealing purpose

Heating metal and cooling it slowly softens it, relieves internal stress and refines grain. It restores machinability after work hardening and prepares steel for further forming.

Lever principle

For balance, load times load arm equals effort times effort arm. A longer effort arm reduces the effort needed, which is why spanners and crowbars have long handles.

Coefficient of friction

The ratio of friction force to normal reaction between two surfaces. Friction force equals the coefficient multiplied by the normal reaction, and it opposes relative sliding.

Vernier least count

The smallest reading a Vernier caliper can show, found as one main scale division minus one Vernier division. A common metric caliper reads to 0.02 millimetres.

Micrometer least count

Screw pitch divided by the number of thimble divisions. A 0.5 millimetre pitch with a 50 division thimble gives 0.01 millimetre, the usual outside micrometer resolution.

Electromagnetic induction

A changing magnetic flux through a coil induces a voltage in it. Generators use this by rotating a coil in a magnetic field, producing alternating current.

Fire extinguisher choice

Water suits solid combustibles only. Foam and carbon dioxide suit flammable liquids, dry powder suits gases, and electrical fires need carbon dioxide, never water.