Kinetic Energy and momentum

Question 1

What is each part of the work done equation measured in?

Work done = force X distance

Answer 1

Work done = j
Force = N
Distance = M

Question 2

What is the units for the power, work done (energy and time equation?

Answer 2

Power = watts
Energy (work done)= joules
Time = seconds

Question 3

A force of 200N pushes a car 30 m, calculate the world done

Answer 3

200N X 30 M = 6000J

Question 4

A drill transfers 3000 J in 15 seconds. What is the power?

Answer 4

3000J / 15 s = 200 W

Question 5

What does gravitational energy depend on? (2)

Answer 5

Mass

Height above ground

Question 6

What is the relationship between the height of an object and the amount of gravitational potential energy?

Answer 6

Directly proportional

Question 7

What are gravitational energy and kinetic energy measured in?

Answer 7

J

Question 8

Ep= m X g X h

A book with a mass of 0.25kg is lifted 2m off the ground. The gravitational field strength is 10 n/kg

What is the change in gravitational potential energy?

Answer 8

Ep= 0.25 kg X 10 X 2 m

= 5 J

Question 9

What does kinetic energy depend on?

Answer 9

Mass

Speed

Question 10

Ek= 1/2 X m X v2

What is the kinetic energy of a 1000 kg car travelling at 5 m/s?

Answer 10

Ek= 1/2 X 1000 kg X 5 squared

Ek= 12500 J

Question 11

What machine transfers gravitational potential energy to kinetic energy and back again?

Answer 11

A pendulum

Question 12

What does a pendulum do?

Answer 12

Transfers gravitational potential energy to kinetic energy and back again

Question 13

How does a pendulum change kinetic and gravitational energy ? (4)

Answer 13

When the Bob is at the highest point on the swing, gravitational potential energy is at its maximum

When it swings downwards, gravitational potential energy is transferred to kinetic energy and the Bob accelerates

When it is at the bottom of its swing, the kinetic energy is at its maximum. Gravitational potential energy is at its minimum.

Kinetic energy is transferred to gravitational potential energy when it swings upwards. It then has no kinetic energy

Question 14

Why does the bob’s swing become lower with each swing on a pendulum ?

Answer 14

Energy is transferred as heat to the surroundings

Question 15

What is momentum?

Answer 15

Quantity of motion

How difficult it is to stop a moving object

Question 16

What is momentum measured in?

Answer 16

P is measured in kg m/s

Question 17

What does momentum depend on? (3)

Answer 17

Mass
Velocity
Direction of travel

Question 18

What is the relationship between the speed of a car and momentum?

Answer 18

Directly proportional

Question 19

P= m X v

What is the momentum of a 5kg object moving with a velocity of 2 m/s ??

Answer 19

P= 5kg X 2 M/s

p = 10 kg m/s

Question 20

What are the 3 things you write for a momentum question?

Answer 20

Equal and opposite forces have equal momentum

Momentum is conserved as the forces transfer the same energy to eachother

Momentum before = momentum after = 0

Question 21

Two railway carriages collide and move off together. Carriage A has a mass of 12,000 kg and moves at 5 m/s before the collision.
Carriage B has a mass of 8,000 kg and is stationary before the collision. What is the velocity of the two carriages ? (4)

Answer 21

1) find momentum before

Carriage A = 12,000 kg X 5 m/s = 60,000 kg m/s

Carriage B = 8,000 kg X 0 m/s = 0 kg m/s

0+60,000 = 60,000 kg m/s.

2) find momentum after
Momentum before = momentum after so 60,000 kg m/s is momentum after

3) find the total mass
12,000 kg + 8,000 kg = 20,000 kg

4) find velocity
P=mXv
Velocity after = 60,000 kg m/s / 20,000kg

Velocity after = 3 m/s

Question 22

What must the total momentum always be?

Answer 22

0

Question 23

How can the momentum be 0 if i through a 6kg ball at 5 m/s ?

Answer 23

The balls momentum = 5 X 6 = 30 kg m/s

So my momentum must be -30 kg m/s

So total momentum = 0

Question 24

A bullet is fired at 100m/s and weighs 10 g. From a gun weighing 2 kg.

What is the velocity of the gun moving backwards?

Answer 24

P= m X v
100m/s X 0.01 kg = 1 kg m/s

P= m X v
1 kg m/s / 2kg = 0.5 m/s

Question 25

What is the backwards motion of a gun called?

Answer 25

Recoil

Question 26

What is an active SAFTEy feature

Answer 26

Devices that keep a car under control to prevent an accident

Question 27

Examples of active SAFTEy features?

Answer 27

Anti lock breaks

Traction control

Question 28

What is a passive SAFTEy feature?

Answer 28

Systems in a car that protect the passengers and driver

Question 29

Examples of passive SAFTEy features.

Answer 29

Air bags

Seat belts