Unit 4: Physics on the Move
Further Mechanics
Term Definition
Elastic Collision (1) - (Total) kinetic energy is conserved
Inelastic Collision (1) - Kinetic energy is not conserved
- Total momentum before a collision = total momentum
Principle of Conservation of
after collision/total momentum remains constant (1)
Momentum (2)
- Providing no external force acts/in a closed system (1)
Which arrow correctly shows the direction of the frictional force on the coin. (1
mark)
- D (1)
Explain how the drum spinning separates water from the wet clothes. (2 marks)
- Water has no resultant/centripetal force OR the clothes experience a centripetal force
from the drum (1)
- Water continues its motion in a straight line/water leaves drum along a tangent (1)
Explain why it is not possible to rotate the mass so that the string is horizontal. (2
marks)
- Weight acts downwards (1)
- There must be a component of tension in the vertical direction/refers to Tcos θ with
cos θ = 0 when horizontal (1)
Consider the vertical and horizontal motion to give an equation in terms of tan
θ . (3 marks)
,- N sin θ = mg (1)
- N cos θ = mv2/r (1)
- Division of vertical by horizontal equation (1)
Explain, in terms of forces, why the aeroplane is able to fly in a circular path. (2
marks)
- Identifies a horizontal component of lift/refers to Lsin θ (1) which acts as a
centripetal force (1)
State how the motion of the ball at C differs from that at B. (2 marks)
- At B the ball is accelerating (1)
- At C ball has zero acceleration/has a constant speed (1)
Explain why, at the instant of release, the sphere stops travelling in a circular path.
(2 marks)
- When released there is no (horizontal) force acting (1)
- Force is needed to change direction/sphere travels in a straight/tangential line (1)
A student suggests: ‘The ISS travels at a constant speed, so, according to Newton’s
laws, there will be no resultant force acting on it.” (3 marks)
- Although speed is constant, velocity is changing since direction is changing (1)
- Therefore ISS is accelerating (1) so by N1/2 there must be a resultant/centripetal force
(1)
,State the position, X, Y or Z, at which the tension will be a maximum and the
position, X, Y or Z, where it will be a minimum. Explain your answers. (4 marks)
- Centripetal force is the resultant force (1)
- Maximum at Z and minimum at X (1)
- At Z, tension T greater than weight/T = mv2/r + W (1)
- At X, tension T is less than the weight/T = mv2/r – W (1)
Explain why the electron moves in the helical path. (2 marks)
- Circular motion in the vertical plane (1)
- Constant velocity in horizontal direction/no force is horizontal direction (1)
Describe how the path would be different if the electron entered the magnetic
field at an angle less than 70 ° . (2 marks)
- The circles would have a smaller radius (1)
- Distance between adjacent loops would increase (1)
Suggest a reason why the total kinetic energy halfway through the collision is less
than the total kinetic energy after the collision. (1 mark)
- Elastic potential energy is stored in the buffers/springs (1)
Describe how you would use the apparatus shown to verify the law of
conservation of momentum. (5 marks)
, - Measure the mass of each glider (1)
- Measure the length of the card (1)
- Recognize the time for the card to pass the light gate (1)
- Calculate the velocity using length of card/time (1)
- Recognize the need to show that m1v1 = (m1 + m2)v (1)
Explain why it is necessary to use a low-friction track to verify the law of
conservation of momentum. (2 marks)
- Law of conservation of momentum only applies when no external force acts (1)
- Friction would be an external force/friction would alter the velocities (1)
The clay is removed and replaced by a metal plate of the same mass. The
experiment is repeated and this time instead of the pellet sticking to the clay, it
bounces backwards from the metal plate. Explain why the speed of the toy car will
now be greater than in the original experiment. (3 marks)
- Mention of momentum (1)
- Pellet bounces back so has negative momentum (1)
- Pellet undergoes a bigger momentum/mass of car is less (1)
The film showed that the pellet bounced back at an angle to the horizontal.
Explain why the car would move even faster if the pellet bounced directly
backwards at the same speed. (1 mark)
- Greater horizontal momentum/force (1)
A student is using a ‘Newton’s Cradle’. Explain what measurements the student
would take and describe how she would use them to investigate whether
momentum had been conserved in this event. (4 marks)
- Measurement of appropriate quantity e.g. velocity and light gates, height and use of PE-
KE formula, distance and time (1)
- Calculate speed (1) on impact (1)
- Statement of how method shows momentum has been conserved (1)
Discuss the observations of the student in terms of energy. (3 marks)
Ball on the right returns and collides with a similar result; repeats itself a
number of times
After a while, middle balls are also moving
Shortly afterwards, the balls all come to rest
- Collisions inelastic/KE is transferred in collisions (1) to internal energy/to sound (1)
- Eventually stops because all energy is transferred (1)
Further Mechanics
Term Definition
Elastic Collision (1) - (Total) kinetic energy is conserved
Inelastic Collision (1) - Kinetic energy is not conserved
- Total momentum before a collision = total momentum
Principle of Conservation of
after collision/total momentum remains constant (1)
Momentum (2)
- Providing no external force acts/in a closed system (1)
Which arrow correctly shows the direction of the frictional force on the coin. (1
mark)
- D (1)
Explain how the drum spinning separates water from the wet clothes. (2 marks)
- Water has no resultant/centripetal force OR the clothes experience a centripetal force
from the drum (1)
- Water continues its motion in a straight line/water leaves drum along a tangent (1)
Explain why it is not possible to rotate the mass so that the string is horizontal. (2
marks)
- Weight acts downwards (1)
- There must be a component of tension in the vertical direction/refers to Tcos θ with
cos θ = 0 when horizontal (1)
Consider the vertical and horizontal motion to give an equation in terms of tan
θ . (3 marks)
,- N sin θ = mg (1)
- N cos θ = mv2/r (1)
- Division of vertical by horizontal equation (1)
Explain, in terms of forces, why the aeroplane is able to fly in a circular path. (2
marks)
- Identifies a horizontal component of lift/refers to Lsin θ (1) which acts as a
centripetal force (1)
State how the motion of the ball at C differs from that at B. (2 marks)
- At B the ball is accelerating (1)
- At C ball has zero acceleration/has a constant speed (1)
Explain why, at the instant of release, the sphere stops travelling in a circular path.
(2 marks)
- When released there is no (horizontal) force acting (1)
- Force is needed to change direction/sphere travels in a straight/tangential line (1)
A student suggests: ‘The ISS travels at a constant speed, so, according to Newton’s
laws, there will be no resultant force acting on it.” (3 marks)
- Although speed is constant, velocity is changing since direction is changing (1)
- Therefore ISS is accelerating (1) so by N1/2 there must be a resultant/centripetal force
(1)
,State the position, X, Y or Z, at which the tension will be a maximum and the
position, X, Y or Z, where it will be a minimum. Explain your answers. (4 marks)
- Centripetal force is the resultant force (1)
- Maximum at Z and minimum at X (1)
- At Z, tension T greater than weight/T = mv2/r + W (1)
- At X, tension T is less than the weight/T = mv2/r – W (1)
Explain why the electron moves in the helical path. (2 marks)
- Circular motion in the vertical plane (1)
- Constant velocity in horizontal direction/no force is horizontal direction (1)
Describe how the path would be different if the electron entered the magnetic
field at an angle less than 70 ° . (2 marks)
- The circles would have a smaller radius (1)
- Distance between adjacent loops would increase (1)
Suggest a reason why the total kinetic energy halfway through the collision is less
than the total kinetic energy after the collision. (1 mark)
- Elastic potential energy is stored in the buffers/springs (1)
Describe how you would use the apparatus shown to verify the law of
conservation of momentum. (5 marks)
, - Measure the mass of each glider (1)
- Measure the length of the card (1)
- Recognize the time for the card to pass the light gate (1)
- Calculate the velocity using length of card/time (1)
- Recognize the need to show that m1v1 = (m1 + m2)v (1)
Explain why it is necessary to use a low-friction track to verify the law of
conservation of momentum. (2 marks)
- Law of conservation of momentum only applies when no external force acts (1)
- Friction would be an external force/friction would alter the velocities (1)
The clay is removed and replaced by a metal plate of the same mass. The
experiment is repeated and this time instead of the pellet sticking to the clay, it
bounces backwards from the metal plate. Explain why the speed of the toy car will
now be greater than in the original experiment. (3 marks)
- Mention of momentum (1)
- Pellet bounces back so has negative momentum (1)
- Pellet undergoes a bigger momentum/mass of car is less (1)
The film showed that the pellet bounced back at an angle to the horizontal.
Explain why the car would move even faster if the pellet bounced directly
backwards at the same speed. (1 mark)
- Greater horizontal momentum/force (1)
A student is using a ‘Newton’s Cradle’. Explain what measurements the student
would take and describe how she would use them to investigate whether
momentum had been conserved in this event. (4 marks)
- Measurement of appropriate quantity e.g. velocity and light gates, height and use of PE-
KE formula, distance and time (1)
- Calculate speed (1) on impact (1)
- Statement of how method shows momentum has been conserved (1)
Discuss the observations of the student in terms of energy. (3 marks)
Ball on the right returns and collides with a similar result; repeats itself a
number of times
After a while, middle balls are also moving
Shortly afterwards, the balls all come to rest
- Collisions inelastic/KE is transferred in collisions (1) to internal energy/to sound (1)
- Eventually stops because all energy is transferred (1)
