6 exam-style questions with full mark schemes and model answers. Write your own answer and the AI examiner marks it against the mark scheme.
Learn this properly: Resultant Forces and EquilibriumA skydiver jumps from a stationary helicopter and falls towards the ground. Shortly after leaving the helicopter the skydiver speeds up, but after some time they fall at a steady terminal velocity. Later they open their parachute and quickly slow down to a new, lower steady speed.
Describe and explain, in terms of the forces acting and Newton's laws of motion, how the skydiver's motion changes from the moment they jump until they are falling at the new steady speed after the parachute opens. (6 marks)
A class investigated Newton's second law by pulling a trolley along a bench with a constant force and measuring its acceleration for different total masses, keeping the pulling force the same each time. Their results are shown below.
| Total mass / kg | Acceleration / m/s² |
|---|---|
| 0.5 | 4.8 |
| 1.0 | 2.4 |
| 1.5 | 1.6 |
| 2.0 | 1.2 |
(a) Using a row from the table, calculate the constant pulling force used in the investigation. Use F=ma. Show your working and give the unit. (3 marks)
(b) State the relationship between acceleration and mass shown by the data when the force is kept constant. (1 mark)
A trolley of mass 2.0 kg is moving along a straight track at a velocity of 3.0 m/s.
(a) Calculate the momentum of the trolley. Use p=mv. Show your working and give the unit. (2 marks)
(b) The trolley collides with and sticks to a stationary trolley of mass 4.0 kg. Using the conservation of momentum, calculate the velocity of the two trolleys immediately after the collision. (1 mark)
A child of weight 300 N sits on one side of a see-saw, a horizontal distance of 1.2 m from the central pivot.
(a) Calculate the moment of the child's weight about the pivot. Use moment=force×perpendicular distance. Show your working and give the unit. (2 marks)
(b) A second child of weight 450 N sits on the other side. Using the principle of moments, calculate the distance from the pivot at which the second child must sit so that the see-saw balances. (1 mark)
A car of mass 1200 kg experiences a resultant forward force of 3600 N.
Calculate the acceleration of the car. Use F=ma. Show your working and give the unit. (2 marks)
An object is said to be in equilibrium.
State what is meant by an object being in equilibrium. (1 mark)