Yr9, Phys- cycle 1

Question 1

What is the formula to work out energy efficiency?

Answer 1

Energy Efficiency = (Useful energy out / Total energy in ) * 100

Question 2

What is the formula for Gravitational Potential Energy (GPE)?

Answer 2

GPE = m * g * h

m- mass (kg)
g- gravitational field (N/kg)
h- change in height (m)

Question 3

What is the formula for Elastic Potential Energy (EPE)?

Answer 3

EPE = 1/2 * k * e(squared)

1/2- half
k- spring constant (N/m)
e- extension past equilibrium

Question 4

Can energy be created or destroyed?

Answer 4

No.

Question 5

True or False?

No matter the amount of energy put in, half the amount of energy comes out in Joules.

Answer 5

False.

No matter how much energy put in, the SAME amount of energy comes out in Joules.

Question 6

What is Gravitational Potential Energy (GPE)?

Answer 6

GPE is energy that is stored by an object when it’s height increases.

Question 7

Calculate the GPE:

m = 10kg
h = 5m

Answer 7

GPE = m * g * h

GPE = 10 * 10 * 5 = 500J

GPE = 500 J

Question 8

A 15kg book is raised 10m above the ground. Calculate the amount of GPE the book has.

Answer 8

GPE = m * g * h

GPE = 15 * 10 * 10 = 1500J

GPE = 1500 J

Question 9

If Sophie climbs a ladder 3.4 m tall, and she has a mass of 4800g, how much GPE has she gained?

If Sophie were to fall, how much KE would she hit the ground with?

Answer 9

Convert 4800g to kg which is 48kg
GPE = m * g * h

GPE = 48 * 10 * 3.4 = 1632J

Sophie would hit the ground w/ 1632J of kinetic energy.

Question 10

What is the Elastic Limit?

Answer 10

The point at which an elastic material will no longer go back to its original length (limit of proportionality)

Question 11

An archer extends her bow by 1m to launch an arrow. If the spring constant of the bow is 20 N/m how much EPE is being stored?

Answer 11

EPE = 1/2 * k * e (squared)

EPE = 1/2 * 20 * 1 (squared) = 10J

EPE = 10 J

Question 12

What is Elastic Potential Energy?

Answer 12

Energy that is stored by an elastic when stretched or compressed.

Question 13

A 50 kg man travels to the moon. When he climbs the 5 m ladder up to his lunar base he gains 400 J of GPE. What is the gravitational field strength on the moon?

Answer 13

Gravitational Field = GPE / (m * h)

Gravitational Field = 400 / (50 * 5) = 1.6 N/kg

Question 14

What is the formula for Kinetic Energy (KE)?

Answer 14

KE = 1/2 * m * v (squared)

1/2- half
m- mass (kg)
v- velocity (m/s)

Question 15

Calculate the KE:

m = 13.5kg
v = 3.2 N/m

Answer 15

KE = 1/2 * m * v (squared)

KE = 1/2 * 13.5 * 3.2 (squared) = 69.12J

Question 16

Calculate the KE:

A car has a mass of 1200kg and the people inside are 220kg and the velocity of the car is 36.6 m/s

Answer 16

KE = 1/2 * m * v (squared)

KE = 1/2 * 1420 * 36.6 (squared)

Question 17

The energy of the school dog Jeoff uses on a breaktime is 400J. He moves at a speed of 11.2 m/s. Calculate his mass.

Answer 17

m = KE/(0.5 * 11.2 (squared))

m = 400/0.5 * 125.44 = 6.38kg

Question 18

What is the formula of work done (WD)?

Answer 18

WD = Force * Distance

WD = n * m

Question 19

What is the formula for Power?

Answer 19

Power = work done / time

Power= WD / T

Question 20

What is specific heat capacity?

Answer 20

The energy needed to raise the temperature of a substance by 1*C

Question 21

What is the formula of specific heat energy (H)?

Answer 21

H = m * c * (change in) t

Question 22

What is thermal conductivity?

Answer 22

The ability of an object to transfer heat energy.

Question 23

Name 7 energy sources.

Answer 23

Solar
Wind
Tidal / Wave
Biomass
Geothermal
Hydroelectric
Fossil Fuels