Newton's laws of motionIB MYP Sciences: Subtopic test

1. 1
   A car of mass 1500 kg is waiting at traffic lights in Singapore. When the light turns green, the engine produces a resultant forward force of 4500 N on the car.

   (a)

   What is the acceleration of the car?

   [1 mark]

   • A0.33 m/s²
   • B6 750 000 m/s²
   • C6000 m/s²
   • D3.0 m/s²

   (b)

   The car later moves along a straight, level road at a steady 20 m/s. Which statement about the horizontal forces on the car is correct?

   [1 mark]

   • AThe forces are balanced
   • BThere is a resultant force in the direction of motion
   • CThe engine force is zero
   • DThe resultant force equals the weight of the car

   (c)

   Explain, using Newton's first law, why passengers lurch forward when the car brakes suddenly.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A skydiver in New Zealand jumps from a plane and falls for some time before opening her parachute. Her weight is 700 N.

   (a)

   Which statement describes the skydiver at the moment she leaves the plane?

   [1 mark]

   • AAir resistance is greater than her weight
   • BThe forces on her are balanced
   • CHer weight is greater than the air resistance, so she accelerates downwards
   • DNo forces act on her

   (b)

   She opens her parachute. Which statement describes the forces immediately afterwards?

   [1 mark]

   • AHer weight increases
   • BAir resistance becomes greater than her weight, so the resultant force is upwards
   • CAir resistance decreases
   • DThe forces stay balanced, so she keeps the same velocity

   (c)

   Explain why the skydiver's speed stops increasing before she opens her parachute.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   Lena, a student in Berlin, investigates how the resultant force on a trolley affects its acceleration. The trolley has a mass of 1.0 kg and runs on a low-friction track. She pulls it with different constant forces and measures its acceleration with a data logger. The accelerations are 0.5 m/s² for 0.5 N, 1.0 m/s² for 1.0 N, 1.6 m/s² for 1.5 N, 2.0 m/s² for 2.0 N and 2.5 m/s² for 2.5 N.

   (a)

   State a testable hypothesis for this investigation, with a scientific reason, and identify one variable that Lena must control.

   [3 marks]

   (b)

   Process the data: calculate force ÷ acceleration for the 2.0 N result, explain what this value represents, identify the result that does not fit the pattern, and state a conclusion.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A government in the Gulf is reviewing its laws on seat belts. In a crash test, a car travelling at 20 m/s is brought to rest in 0.10 s. A crash-test dummy of mass 70 kg, wearing a seat belt, stops with the car.

   (a)

   Discuss the social, economic and ethical implications of making seat belts compulsory in all seats of all vehicles, with reference to Newton's first law.

   [6 marks]

   (b)

   Calculate the deceleration of the dummy and the force that the seat belt exerts on it. State the force that the dummy exerts on the seat belt, and explain how you know.

   [6 marks]

   Total for question 4: 12 marks

End of questions