1. 1
   Two shoppers push a loaded shopping trolley of mass 25 kg along a flat, straight supermarket aisle. One shopper pushes forwards with a force of 30 N, while friction from the wheels acts backwards on the trolley with a force of 12 N. Both forces act along the same straight line.

   (a)

   Which quantity, applied to the shopping trolley in this scenario, is a vector quantity?

   [1 mark]

   • AThe pushing force of 30 N
   • BThe mass of the trolley
   • CThe time taken to push it
   • DThe total distance travelled

   (b)

   Which equation would correctly be used to find the acceleration of the trolley once the resultant force on it is known?

   [1 mark]

   • AW = Fs
   • BF = ma
   • Cp = mv
   • DM = Fd

   (c)

   Calculate the resultant force acting on the trolley, stating its direction.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A fridge magnet holds a shopping list against the metal door of a fridge, attracting it before the two objects touch. Separately, a person presses the fridge door shut with their hand until it clicks closed.

   (a)

   Which force holds the magnet against the fridge door before the door is touched?

   [1 mark]

   • AFriction
   • BNormal contact force
   • CMagnetic force
   • DTension

   (b)

   Which of the following is a contact force?

   [1 mark]

   • AMagnetic force
   • BGravitational force
   • CElectrostatic force
   • DThe force of the person's hand pushing the door

   (c)

   State two differences between contact forces and non-contact forces, using the magnet and the hand pushing the door as examples.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A physiotherapist tests a rubber resistance band used in a patient's rehabilitation exercises. She hangs the band vertically and adds weights, recording the extension while the band stays within its limit of proportionality. When a force of 15 N is applied, the band stretches by 0.05 m.

   (a)

   Calculate the spring constant of the resistance band. State whether the band shows elastic or inelastic deformation while it obeys this relationship, and explain your answer.

   [3 marks]

   (b)

   The physiotherapist then applies a force of 24 N to the band, keeping it within the limit of proportionality. Calculate the extension produced by this force, and the elastic potential energy stored in the band at this extension.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A theatre technician uses a long metal bar (a lever) resting on a fixed support (the pivot) to lift one end of a heavy stage platform, so that a wheeled trolley can be slid underneath. A colleague suggests that, for future tasks, a system of two differently sized gears connected by a chain could be used instead of the lever bar to transmit the lifting force.

   (a)

   The platform exerts a downward force of 900 N on the bar at a distance of 0.3 m from the pivot. Explain the principle of moments and use it to calculate the minimum force the technician must apply, 1.8 m from the pivot on the other side, to just balance the bar. Then explain why using a longer bar makes the technician's job easier, in terms of moments.

   [6 marks]

   (b)

   Explain how a simple lever, like the bar the technician used, and a system of gears can both be used to transmit the rotational effect of a force. Discuss one advantage and one disadvantage of using a system of gears instead of a single lever bar for a task like lifting the stage platform.

   [6 marks]

   Total for question 4: 12 marks

5. 5
   A hiker compares two pairs of footwear for walking across soft snow: ordinary boots with a total sole contact area of 0.05 m^2, and snowshoes with a total contact area of 0.5 m^2. The hiker's weight, including equipment, is 750 N.

   (a)

   Which equation should be used to calculate the pressure the hiker exerts on the snow?

   [1 mark]

   • Ap = hρg
   • Bp = Fs
   • Cp = ma
   • Dp = F/A

   (b)

   Snowshoes have a much larger contact area than ordinary boots. For the same weight, what effect does this have on the pressure exerted on the snow?

   [1 mark]

   • ADecreases the pressure
   • BIncreases the pressure
   • CHas no effect on the pressure
   • DReduces the pressure to zero

   (c)

   Calculate the pressure the hiker exerts on the snow while wearing the snowshoes.

   [2 marks]

   Total for question 5: 4 marks

6. 6
   An open-water swimmer completes a training swim around a triangular course marked by three buoys in a lake, returning to her starting point. She swims a total distance of 1500 m around the course in 1200 s, but her straight-line displacement for the whole swim is 0 m.

   (a)

   Which quantity describes the 1500 m the swimmer covers while swimming around the buoys?

   [1 mark]

   • ADisplacement
   • BDistance
   • CVelocity
   • DAcceleration

   (b)

   Why is the swimmer's displacement for the whole swim 0 m, even though she swims 1500 m?

   [1 mark]

   • AShe did not move during the swim
   • BDistance and displacement are always equal in size
   • CShe returned to her starting point, so there is no overall change in position
   • DShe swam too slowly for her position to change

   (c)

   Calculate the swimmer's average speed for the training swim.

   [2 marks]

   Total for question 6: 4 marks

7. 7
   A quality-control technician drops a small steel ball bearing into a tall measuring cylinder filled with a viscous liquid, glycerine, to test the liquid's properties. The ball accelerates from rest as it begins to fall, but its velocity-time graph shows the line becoming less steep before flattening out completely as the ball continues to fall through the liquid. The ball bearing has a mass of 0.02 kg, and during the first 0.1 s of falling its velocity increases from 0 m/s to 0.4 m/s.

   (a)

   Explain, in terms of the forces acting on the ball bearing, why its velocity-time graph flattens out (why the line has zero gradient) as it continues to fall through the glycerine.

   [3 marks]

   (b)

   The ball bearing has a mass of 0.02 kg. During the first 0.1 s of falling, before it reaches terminal velocity, its velocity increases from 0 m/s to 0.4 m/s. Calculate the ball's acceleration during this time, and the resultant force acting on it, stating the equations used.

   [4 marks]

   Total for question 7: 7 marks

8. 8
   A go-kart, including its driver, has a total mass of 250 kg and is travelling at 12 m/s along a straight section of track when the driver sees a slower kart ahead and reacts by braking. The driver's reaction (thinking) time is 0.6 s, and the kart then decelerates uniformly, coming to a complete stop 2.0 s after the brakes are applied.

   (a)

   Calculate the go-kart's total stopping distance, showing the thinking distance and braking distance separately, and explain two factors (other than reaction time) that could increase the braking distance on a go-kart track.

   [6 marks]

   (b)

   The go-kart's mass is 250 kg and its velocity decreases from 12 m/s to 0 m/s in 2.0 s as it brakes. Calculate the rate of change of momentum of the go-kart during braking, and explain, using this idea, why go-karts, like cars, are fitted with safety features such as padded seat restraints that increase the time taken for a driver to stop in a collision.

   [6 marks]

   Total for question 8: 12 marks

End of questions