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Forces, Newton's laws and free-body diagramsEdexcel A-Level Physics: Flashcards

What these 13 flashcards ask

  • What does a free-body diagram show?
  • State Newton's first law.
  • State Newton's second law.
  • What is the formula for weight?
  • What are the units of gravitational field strength g?
  • Why is the acceleration of a skydiver at the start of a fall equal to g?
  • Describe how terminal velocity is reached.
  • What happens to the resultant force and acceleration as an object approaches terminal velocity?
  • List the four features of a Newton's third law pair.
  • Which force pairs with the weight of an object?
  • A book rests on a table. Why are weight and the contact force not a third law pair?
  • A passenger in a lift accelerating upwards at a: what is the contact force N?
  • Can an object move at constant velocity with forces acting on it?

Exam questions on Forces, Newton's laws and free-body diagrams

  1. A book of mass 0.80 kg rests on a horizontal table.
    Calculate the weight of the book and explain, using Newton's first law, why the contact force from the table has this same size.2 marks
  2. A car of mass 1200 kg accelerates in a straight line from rest along a level road. Its engine produces a driving force of 3600 N and the resistive forces on the car total 600 N.
    At a higher speed the resistive forces rise to 3600 N while the driving force is unchanged. Describe and explain the motion of the car from this point.2 marks
  3. A skydiver of mass 80 kg falls vertically with her parachute closed. At one instant her speed is 30 m s⁻¹ and the air resistance on her is 360 N.
    Calculate the acceleration of the skydiver at this instant.3 marks
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Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).