Force, Work And Power And Turning Forces, Centre Of Gravity

Question 1

Examples of forces

Answer 1

Push, pull, weight and friction.

Question 2

Forces are measured using

Answer 2

A spring balance

Question 3

Friction

Answer 3

Friction is a force which prevents easy movement between two objects in contact

Question 4

Weight

Answer 4

The weight of an object is the force of gravity acting on it.

Question 5

Hooke’s law

Answer 5

Hooke’s law states that the extension of a spring depends on the size of the weight (force) attached to it

Question 6

A graph of spring extension

Answer 6

Against the weight (force) attached to it, gives a straight line through the origin (0,0)

Question 7

Energy

Answer 7

Is the ability to do work

Question 8

Work

Answer 8

Is done when a force moves an object. Work is measured in joules.

Question 9

Force

Answer 9

A force is anything which causes an object to move or change its velocity.

Question 10

Power

Answer 10

It is the rate at which is done. Power is the amount of work done in one second. It is measured in watts. Work done / time taken

Question 11

Weight is a force…

Answer 11

measured in newtons

Question 12

The force of gravity on Earth

Answer 12

is 10N on every 1kg of mass

Question 13

To find the weight on Earth

Answer 13

multiply the mass (in kg) by 10

Question 14

Moment

Answer 14

the moment of a force is the turning effect of a force. Moment = (Force) x (Distance from the fulcrum)

Question 15

Lever

Answer 15

Any rigid body which is free to turn about a fixed point called the fulcrum

Question 16

Examples of lever are:

Answer 16

door, door handle, pliers, sissors, metre stick, screwdriver (used to open paint tin)

Question 17

The Law Of The Lever

Answer 17

states that when a lever (eg. metre stick) is balanced the total clockwise moments equal the total anticlockwise moments

Question 18

The centre of gravity

Answer 18

of an object is the point through which all the weight of the object appears to act (ie. the centre of its weight)

Question 19

Stable equilibrium

Answer 19

is present if when an object is slightly tilted, its centre of gravity is raised , and it goes back to the original release

Question 20

Unstable equilibrium

Answer 20

is present if when an object is slightly tilted, its centre of gravity is lowered, and it takes a new position when released (ie. it falls on its side)

Question 21

Neutral equilibrium

Answer 21

is present if when an object is moved, its centre of gravity is neither raised nor lowered. The object never becomes unstable - it does not fall over and just takes up a new position where it is still in neutral equilibrium