Equations

Question 1

Equation for finding the energy in an objects gravitational potential energy store

And what do the letters represent? Don’t forget unit’s!

Answer 1

Ep= m x g x h 
m = Mass (Kg)
g = Gravity (N/Kg)
h= height (m)

Question 2

Calculate the GPE store of the rock

g = 9.8N/kg mass 75kg Height 4m

Answer 2

Ep= m g h

Ep = 75 x 9.8 x 4 = 2940J
Kg) ( J ) ( height in m ) ( total G P E store of rock

Question 3

An astronaut lifts a golf ball 2.6 m above the moon surface. If the golf ball’s mass is 200 g, find the gravitational potential energy stored assume g = 1.63 N/kg

Answer 3

Ep= m g h 
Ep = 0.2Kg x 1.63 x 2.6 = 0.85J

Question 4

How many…?

a) cm in a meter?
b) g in a Kg?
c) J in a KJ?

Answer 4

How many…?

a) 100
b) 1,000
c) 1,000

Question 5

Give the equation for finding the energy stored in an objects kinetic energy store?

And what do the letters within the it represent? Don’t forget units!

Answer 5

Ek = 0.5 x m x v²

Mass (Kg)
Velocity (m/s)

Question 6

Find the kinetic energy store of an object of mass 4 kg and velocity 3m/s.

velocity = 3m/s
Mass= 4kg

Answer 6

Ek= 1/2m x v²
Ek=0.5 x 5 x (3 2 )
Ek=0.5 x 4 x 9 Mass = 4kg
=18J

Question 7

A ball is moving with a velocity of 500cm/s. Its mass is 0.25Kg Dartcalculate its kinetic energy store.

Answer 7

Ek=1/2mv²
Ek=0.5 x 0.25 x 52
Ek=0.63J

Question 8

Give the equation for finding the energy in an object’s elastic potential energy store?

And want to do the letters with a net represent? Don’t forget units!

Answer 8

Ee = 1/2 x k x e²

Spring constant (N/m)

Extension (m)

Question 9

Robert stretches a spring with a spring constant of 3 N/m until it is extended by 50 cm.what is the elastic potential energy stored by the spring?

Answer 9

Es = 1/2 x k x e²

Ee = 0.5 x 3 x 0.5²
Ee = 0.38J

Question 10

How much elastic potential energy does a spring store when it is compressed by 0.2 m if it has a spring constant of 5 N/m?

Answer 10

Ee = 1/2 x k x e²

Ee = 0.5 x 5 x 0.2²
Ee = 0.1J

Question 11

A cable car of mass 4500 kg is suspended 1.2 km above the earth surface. find the gravitational potential energy stored

Answer 11

Ep = m g h

Ep= 4,500 x 9.8 x 1200
Ep= 52,920,000J

Question 12

Define gravitational potential energy store

Answer 12

When an object is lifted in a gravitational field, energy is transferred to a gravity store. this store is called gravitational potential energy.

Question 13

A spaceship of mass 9,950kg lands at the top the top of the Mountain 5.5km above Jupiter’s surface. Acceleration due to gravity on Jupiter is 24.5N/kg. Find the gravitational potential energy stored

Answer 13

Ep = m g h

Ep = 9950 x 24.5 x 5500
Ep = 1,340,762,500J

Question 14

What does g measure? And what number us used for g in the AQA exams?

Answer 14

Weight is a force due to the pull of gravity on an object. Weight is a force and so is measured in newtons(N). On earth, The downward force of gravity on a 1 Kg mass is 10 N. This is called the gravitational field strength (g). The AQA measure of g is Earth (g = 9.8 N/Kg).

Question 15

Find the gravitational potential energy stored when an apple of mass 0.23kg, 65m above the Earth’s surface.

Answer 15

Ep = m g h

Ep= 0.23 x 9.8 x 65
Ep= 147J

Question 16

HT A helicopter hovers 568m above a field and 96kJ of gravitational potential energy is stored. Assuming g = 9.8 N/kg, find the helicopter’s mass.

Answer 16

Ep = m g h
m = Ep/gh
m = 96,000 / (9.8x568
m =17.2kg

Question 17

HT find the height of a crow of mass 860g flying above the Earth’s surface if the gravitational potential energy stored is 5,643J. Assume g = 9.8N/kg.

Answer 17

Ep = m g h
h = Ep / mg 
h = 5,643 / (0.86 x 9.8)
h = 670m