2.3 Work, Energy And Momentum

Question 1

What is work done? Unit?

Answer 1

Energy transferred

Joules (J)

Question 2

Work done to overcome friction is mainly transferred into energy by what?

Answer 2

Heating

Question 3

What is gravitational potential energy?

Answer 3

Energy stored in an object because of its position in the earths gravitational field

Question 4

When does an object gain Gravitational potential energy?

Answer 4

When it is moved vertically upwards

Question 5

What is the gravitational potential energy equal to when it is moved vertically up?

Answer 5

Equal to work done on it by the lifting force

Question 6

Unit for…
Gravitational potential energy
Gravitational field strength

Answer 6

Joules (J)

Newtons per kilogram (N/kg)

Question 7

What is power?

Answer 7

The rate of transfer of energy
Or
Work done in a given time

Question 8

Unit of power?

Answer 8

Watts (W)

Question 9

What do all moving objects have?

Answer 9

Kinetic energy

Question 10

What is momentum?

Answer 10

A property of moving objects

Question 11

What happens to momentum in a closed system?

Answer 11

It is conserved in a closed system i.e no other external force are involved

Question 12

Momentum involves mass and velocity, can momentum be negative? Explain?

Answer 12

Velocity can be negative if it goes in the opposite direction
Therefore momentum can be as well

Question 13

Unit of momentum?

Answer 13

Kg m/s

Question 14

What happens in an explosion?

Answer 14

Two objects move apart with equal and opposite momentum
As
One momentum is positive and the other is negative
Making the total monument zero

Question 15

What is an example of an explosion?

Answer 15

A gun
The bullet fires off with momentum in one direction
The gun recoils with equal momentum in the opposite direction

Question 16

What happens to momentum in a collision?

Answer 16

Often becomes zero during impact

Question 17

If the impact time is short what happens to the force?

Answer 17

It is large

Question 18

If the impact time is longer what happens to the force?

Answer 18

It decreases

Question 19

What does a crumple zone do in a car?

Answer 19

It folds in a collision

Increasing the impact time so it reduces the force on the car and the people in it

Question 20

What other safety features do cars have?

Answer 20

Airbags: spread the force across a wider surface area

Seat belt: increases impact time which reduces the force