Mechanics 2

Question 1

Centre of Gravity

Answer 1

A complicated body can be simplified by using a single point where all the weight of the body can be considered to act.

Question 2

Moment of a force

Answer 2

The product of the force and the perpendicular distance between the axis of rotation and the line of action of the force.

Question 3

The Principle of moments

Answer 3

“If a system is in equilibrium, the sum of the clockwise moments must equal the sum of the anticlockwise moments about any point.”

Question 4

Gravitational field strength (g)

Answer 4

Equal to 9.81 N kg-1 at the Earth’s surface.
It is the force that acts on each kilogram of a body at the surface of the Earth.
Formula is g = F/m.

Question 5

Principle of conservation of energy

Answer 5

“Energy cannot be created or destroyed, it can only be transferred from one form to another”

Question 6

Kinetic Energy (Ek)

Answer 6

Energy due to motion

Given by: Ek = ½ m v2

Question 7

Gravitational Potential Energy

Answer 7

Gravitational Potential Energy (GPE) is the energy stored by an object due to its position (height).
The Formula for finding the g.p.e. transferred close to the Earth’s surface is: ∆Egrav = m g ∆h

Question 8

Work or Work done

Answer 8

Work is done on an object when a force is used to transfer energy to it. Energy transferred.
Work done = force × distance moved in direction of force.
Formula is: ∆W = F∆s

Question 9

Power

Answer 9

“The rate that work is done”
Power = work done ÷ time taken
Power = Force x Velocity

Question 10

Efficiency

Answer 10

Used to describe what fraction of the energy transferred is transferred as useful energy
Efficiency = (Useful energy out of transfer/total energy put in) x 100