P2 Topic 4 - Momentum, Energy, Work And Power

Question 0

What is thinking distance affected by?

Answer 0

Reaction time - tiredness, drugs, alcohol, old age

Speed of the car - faster speed -> longer distance travelled

Question 1

Define thinking distance.

Answer 1

The distance travelled by the car in the time taken for the driver to notice the hazard and start pressing the brakes.

Question 2

Define braking distance.

Answer 2

The distance travelled by the car in the time it takes for the car to stop since the brakes are first applied.

Question 3

What affects braking distance?

Answer 3

Speed of the car
Mass of the car
Quality of brakes
Road conditions
Quality of tyres

Question 4

How do you calculate momentum?

Answer 4

Momentum = Mass x Velocity

kg m/s = kg x m/s

Question 5

What is the conservation of momentum?

Answer 5

The total momentum before and after a collision is equal.

Question 6

Change the equation F = ma to include momentum.

Answer 6

F = ma     (a = v-u/t)
F = m x (v - u)/t
F = mv - mu /t

Rate of change of momentum = Force

Question 7

What is the equation for work done?

Answer 7

Work Done = Force x Distance moved in direction of force

E = F x D

Question 8

What is the equation for power?

Answer 8

Power = Work Done / Time Taken

Question 9

What is the equation for kinetic energy?

Answer 9

KE = 1/2 x mass x velocity^2

Question 10

What is the equation for gravitational potential energy?

Answer 10

GPE = mass x gravitational field strength x height
Joules = kg x N/kg x m

Question 11

What is the Principle of Conservation of Energy?

Answer 11

Energy can never be created nor destroyed - only transferred from one form to another.

Energy is only useful when it’s transferred from one form to the other.