1. 1
   A technician in a school laboratory sets up a trolley of mass 2 kg on a smooth, horizontal air track, eliminating friction. A string is attached to the trolley, passes over a frictionless pulley at the end of the track, and is connected to a hanging weight. When released, the string exerts a constant, resultant force of 4 N on the trolley, and the trolley begins to accelerate from rest along the track.

   (a)

   Which of Newton's laws of motion correctly describes the trolley's motion once the resultant force is applied?

   [1 mark]

   • ANewton's first law: the trolley moves at constant velocity since the resultant force is zero
   • BNewton's second law: the trolley accelerates because a non-zero resultant force acts on it
   • CNewton's third law: the trolley experiences an equal and opposite reaction force from the pulley
   • DNewton's first law: the trolley remains at rest because the resultant force is balanced

   (b)

   In which direction does the trolley's acceleration act?

   [1 mark]

   • AIn the same direction as the resultant force from the string
   • BIn the opposite direction to the resultant force from the string
   • CPerpendicular to the resultant force from the string
   • DThe acceleration direction cannot be determined without a diagram

   (c)

   Calculate the acceleration of the trolley while the 4 N resultant force acts on it.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   An astronaut with a mass of 80 kg travels from Earth, where the gravitational field strength is 10 N/kg, to the surface of the Moon, where the gravitational field strength is 1.6 N/kg. The astronaut's mass does not change during the journey, but their weight does.

   (a)

   Which statement correctly describes the astronaut's weight?

   [1 mark]

   • AWeight is a scalar quantity measured in kilograms
   • BWeight and mass are the same physical quantity
   • CWeight is constant everywhere in the universe
   • DWeight is the force of gravity acting on an object, measured in newtons

   (b)

   Which instrument would correctly be used to measure the astronaut's weight?

   [1 mark]

   • AA top-pan balance calibrated in kilograms
   • BA metre ruler
   • CA calibrated newtonmeter (spring balance)
   • DA stopwatch

   (c)

   Calculate the astronaut's weight on the surface of the Moon.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A model car of mass 1.5 kg moves at a constant speed of 2 m/s around a circular track of constant radius. It then collides head-on with a second, identical model car of mass 1.5 kg that is stationary. On collision, the two cars stick together and move off with a common velocity as a single body.

   (a)

   While the car moves at constant speed around the circular track, explain why its velocity is continually changing and identify the direction of the resultant force needed to keep it moving on the circular path.

   [3 marks]

   (b)

   Using the principle of conservation of momentum, calculate the common velocity of the two cars immediately after the collision, and use Newton's third law to explain the forces acting between the two cars during the collision.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A driving instructor is teaching a student about stopping distances. The student's car is travelling at 15 m/s on a dry, well-maintained road. The instructor explains that stopping distance is the sum of thinking distance and braking distance, and that various factors affect each of these depending on the conditions and the driver.

   (a)

   Explain how the driver's reaction time, the mass and speed of the vehicle, and the condition of the road and brakes each affect the thinking distance and braking distance of a vehicle.

   [6 marks]

   (b)

   The student's car decelerates from 15 m/s to rest in 3 seconds during an emergency stop. Estimate the average deceleration and evaluate the size of the force needed to bring the car (mass 1200 kg) to a stop in this time, discussing the dangers this could pose to the occupants.

   [6 marks]

   Total for question 4: 12 marks

End of questions