Speed, velocity and accelerationIB MYP Physics: Subtopic test

1. 1
   A runner in Kingston, Jamaica, completes one 400 m lap of an oval running track in 50 s. The track has two straight sections and two curved bends. A stopwatch measures the time for the whole lap.

   (a)

   What is the runner's average speed for the lap?

   [1 mark]

   • A0.125 m/s
   • B350 m/s
   • C450 m/s
   • D8 m/s

   (b)

   Which statement about the runner's average speed of 8 m/s is correct?

   [1 mark]

   • AShe ran at exactly 8 m/s at every instant
   • BIt is the total distance divided by the total time, and her speed at a particular instant could be higher or lower
   • CIt is her speed as she crossed the finish line
   • DIt is the same thing as her velocity

   (c)

   Even if the runner keeps a constant speed of 8 m/s, explain why her velocity changes as she runs round a bend.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A train leaves a station in Mumbai. It accelerates uniformly from rest to 20 m/s in 40 s on a straight track. Later, approaching the next station, it brakes uniformly from 20 m/s to rest in 10 s.

   (a)

   What is the acceleration of the train as it leaves the station?

   [1 mark]

   • A800 m/s²
   • B2 m/s²
   • C0.5 m/s²
   • D60 m/s²

   (b)

   What is the acceleration of the train as it brakes?

   [1 mark]

   • A−2 m/s²
   • B+2 m/s²
   • C−0.5 m/s²
   • D−200 m/s²

   (c)

   Calculate the speed of the train 24 s after it leaves the station.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A student in Lagos investigates free fall. She drops a card 12.0 cm long through two light gates, one above the other. The first light gate records that the card blocks the beam for 0.060 s. The second light gate records that the card blocks the beam for 0.020 s. The time for the card to fall from the first light gate to the second is 0.40 s. The accepted value for the acceleration of free fall is 10 m/s².

   (a)

   Calculate the speed of the card as it passes through the first light gate.

   [3 marks]

   (b)

   Calculate the acceleration of the card between the two light gates and say whether the result agrees with the accepted value for free fall.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A council in Abu Dhabi is thinking of installing average-speed cameras on a motorway. Two cameras 6.0 km apart record when each vehicle passes, and a computer works out its average speed in between. The speed limit is 33 m/s. A van passes the first camera at 14:00:00 and the second camera at 14:02:30.

   (a)

   Calculate the van's average speed between the two cameras in m/s. State whether the van broke the speed limit and explain why this means it must have been going faster than the limit at some instant.

   [6 marks]

   (b)

   Discuss and evaluate whether the council should install average-speed cameras on all of its motorways.

   [6 marks]

   Total for question 4: 12 marks

End of questions