Mechanics Definitions

Question 0

Define the term ‘couple’

Answer 0

Two equal but opposite forces

Question 1

State the principle of moments

Answer 1

When an object is in equilibrium the sum of the clockwise moments equals the sum of the anticlockwise moments

Question 2

Define braking distance

Answer 2

The distance travelled by the car after the brakes are applied until the car stops

Question 3

Define the torque of a couple

Answer 3

Torque = one of the forces x perpendicular distance between the forces

Question 4

State hooke’s law

Answer 4

The extension is directly proportional to the force applied, as long as the elastic limit is not exceeded

x = kf

Question 5

Define power

Answer 5

Power = work done / time

Question 6

Define the youngster modulus of a material and state the condition when it applies

Answer 6

Young’s modulus = stress / strain

It is obeyed as long as you don’t exceed the elastic limit of the material

Question 7

Define velocity

Answer 7

Velocity is the rate of change of displacement

Question 8

Define centre of gravity

Answer 8

The point at which the entire weight of the body appears to act

Question 9

Define the watt

Answer 9

1 joule (of work) per second

Question 10

Define work done by a force

Answer 10

Force x distance moved in the direction of the force

Question 11

Define moment of a force

Answer 11

Moment = force x perpendicular distance to the pivot

Question 12

Define acceleration

Answer 12

Acceleration is the rate of change of velocity

Question 13

Define the force constant of a spring

Answer 13

The force per unit extension of the spring

k = f/x

Question 14

State the principle of conservation of energy

Answer 14

In a closed system, energy cannot be created or destroyed, only converted from one form to another.

Question 15

Define density

Answer 15

Density = mass / volume

Question 16

Define a material’s “elastic limit”

Answer 16

The material is permanently deformed when the force/stress is removed.

Question 17

Explain what is meant by “plastic deformation”

Answer 17

The material is permanently deformed when the force / stress is removed

Question 18

Define the ultimate tensile strength of a material

Answer 18

The maximum stress a material can withstand before braking

Question 19

What does it mean to describe a material as brittle

Answer 19

A brittle material does not have a plastic region. It breaks at the elastic limit

Question 20

Define the Newton

Answer 20

The force when a 1kg mass is accelerated at a rate of 1m/s^2

Question 21

Write a word equation for the kinetic energy

Answer 21

Kinetic energy = 1/2 x mass x speed^2

Question 22

Define thinking distance

Answer 22

The distance travelled by a driver from when the driver sees the problem and the brakes are applied.

Question 23

Define a vector quantity and give one example

Answer 23

A quantity with both magnitude and direction.

Examples are: displacement, velocity, acceleration, force, weight