T4 W4 (14.3.24) RM

Question 1

What does ‘work done’ mean?

Give examples

Answer 1

When energy is transferred

Lighting up a room, putting a book on a shelf

Question 2

What is the equation for work done?

Answer 2

Work done = force x distance

Question 3

Car of kinetic energy 240,000 joules brakes and stops in 100 metres. What is the average breaking force?

Answer 3

240,000J / 100 = 2400N

Question 4

Meteor of kinetic energy 8.4 x 10^6 J hits the earth. If the impact force was 42KN calculate the depth of the impact.

Answer 4

8.4 x 10^6 / 42,000 = 200 metres

42KN = 42,000

Question 5

What is the equation for Gravitational potential energy? Explain what the letters mean.

Answer 5

GPE = mgh
* GPE = energy (joules)
* m = mass (kg)
* g = gravitational field strength (N/KG)
* h = height (metres)

Question 6

Calculate your own GPE stood on the desk

Use 60kg for mass

Answer 6

60kg x 10N/kg x 0.8 = 460 J

Question 7

Calculate the GPE of someone standing on Mt. Everest

Use 60kg as mass

Use 10,000 metres as height

Answer 7

60 x 10 x 10,000 = 6,000,000

Question 8

What is the gravitational field strength on earth?

Answer 8

Approximately 10 N/kg

Question 9

What is the equation for kinetic energy? Explain what the letters mean.

Answer 9

KE = 1/2 mv^2
* KE = energy (Joules)
* m = mass (kg)
* v = velocity (speed, m/s)

Question 10

Calculate toddler’s KE if they are moving at 3 m/s, with a mass of 20kg

Answer 10

1/2 x 20kg x 3^2 = 90 J

Question 11

Calculate KE of a cyclist of mass 80kg and a speed of 15 m/s

Answer 11

1/2 x 80 x 15^2 = 9000 J

Question 12

Calculate KE of a formula one car of mass 650kg and a speed of 375 (100 m/s)

Answer 12

1/2 x 650kg x 100^2 = 3.25 x 10^6