Kinetic Energy and momentum Flashcards
What is each part of the work done equation measured in?
Work done = force X distance
Work done = j
Force = N
Distance = M
What is the units for the power, work done (energy and time equation?
Power = watts
Energy (work done)= joules
Time = seconds
A force of 200N pushes a car 30 m, calculate the world done
200N X 30 M = 6000J
A drill transfers 3000 J in 15 seconds. What is the power?
3000J / 15 s = 200 W
What does gravitational energy depend on? (2)
Mass
Height above ground
What is the relationship between the height of an object and the amount of gravitational potential energy?
Directly proportional
What are gravitational energy and kinetic energy measured in?
J
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?
Ep= 0.25 kg X 10 X 2 m
= 5 J
What does kinetic energy depend on?
Mass
Speed
Ek= 1/2 X m X v2
What is the kinetic energy of a 1000 kg car travelling at 5 m/s?
Ek= 1/2 X 1000 kg X 5 squared
Ek= 12500 J
What machine transfers gravitational potential energy to kinetic energy and back again?
A pendulum
What does a pendulum do?
Transfers gravitational potential energy to kinetic energy and back again
How does a pendulum change kinetic and gravitational energy ? (4)
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
Why does the bob’s swing become lower with each swing on a pendulum ?
Energy is transferred as heat to the surroundings
What is momentum?
Quantity of motion
How difficult it is to stop a moving object
What is momentum measured in?
P is measured in kg m/s
What does momentum depend on? (3)
Mass
Velocity
Direction of travel
What is the relationship between the speed of a car and momentum?
Directly proportional
P= m X v
What is the momentum of a 5kg object moving with a velocity of 2 m/s ??
P= 5kg X 2 M/s
p = 10 kg m/s
What are the 3 things you write for a momentum question?
Equal and opposite forces have equal momentum
Momentum is conserved as the forces transfer the same energy to eachother
Momentum before = momentum after = 0
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)
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
What must the total momentum always be?
0
How can the momentum be 0 if i through a 6kg ball at 5 m/s ?
The balls momentum = 5 X 6 = 30 kg m/s
So my momentum must be -30 kg m/s
So total momentum = 0
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?
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
