Motion and forces

Question 1

State and explain the acceleration of a falling object on earth

Answer 1

• 10 m/s

- Due to earth’s gravitational field strength

Question 2

Describe Newton’s third law

Answer 2

• Every action has an equal and opposite reaction

Question 3

Explain how balanced and unbalanced forces affect an object’s motion

Answer 3

• Balanced forces acting on a moving object cause it to
  move at a constant speed (resultant force = 0)
• Balanced forces acting on a stationary object cause it to remain still (resultant force = 0)
• Unbalanced forces acting on an object cause it to accelerate (resultant force = >0)
  (a change in direction is also an acceleration)

Question 4

Show how to turn the formula for momentum into a formula triangle (momentum = mass x velocity)

Answer 4

• Momentum (kg m/s) = Mass (kg) x Velocity (m/s)

Question 5

Explain why large changes in momentum are dangerous in a collision

Answer 5

• Change in Momentum (kg m/s) / time (s) = Resultant Force (N)
• This tells us the force an object experiences will be large if:
  a) The change of momentum is large
  b) The time taken for the change to occur is small

Question 6

State how we calculate overall stopping distance

Answer 6

• Thinking Distance + Braking Distance = Stopping Distance

Question 7

List three factors that affect braking and thinking distance

Answer 7

• Thinking distance is increased by tiredness and alcohol.
  Decreased by caffeine.
• Braking distance is increased by worn tyres and wet/icy roads.
  Decreased by grit on roads.

Question 8

Name three safety features in cars designed to reduce force on passengers

Answer 8

• Seat belts
• Crumple zone
• Air bag