1. Breakdown of Exam Style Questions
Force Revision
Breakdown of Exam Style Questions

2. Given this what can you say about P and Q?
Particles P and Q are attached to the ends of a light inextensible string which passes over a smooth pulley. The system is held at rest with the string taut and its straight parts vertical. Both particles are at a height of 0.36m above the floor. The system is released an P begins to fall, reaching the floor after 0.6s.
Given this what can you say about P and Q?
That the mass of P is greater than Q
P Q

3. What is the acceleration of P as it falls?
Particles P and Q are attached to the ends of a light inextensible string which passes over a smooth pulley. The system is held at rest with the string taut and its straight parts vertical. Both particles are at a height of 0.36m above the floor. The system is released an P begins to fall, reaching the floor after 0.6s.
What is the acceleration of P as it falls?
Given that s = 0.36, t = 0.6, and u = 0, you can solve for a = 2 m/s2
P Q

4. Particles P and Q are attached to the ends of a light inextensible string which passes over a smooth pulley. The system is held at rest with the string taut and its straight parts vertical. Both particles are at a height of 0.36m above the floor. The system is released an P begins to fall, reaching the floor after 0.6s.
What is the time difference between when P has an acceleration of 2 m/s2 and when there is no tension in the rope?
P Q
In that case the acceleration would just be gravity, or
-10m/s2, s = 0.36 and u = 0. This gives you t = 0.27

5. If the mass of P is 0.45kg then what is the tension in the string?
Particles P and Q are attached to the ends of a light inextensible string which passes over a smooth pulley. The system is held at rest with the string taut and its straight parts vertical. Both particles are at a height of 0.36m above the floor. The system is released an P begins to fall, reaching the floor after 0.6s.
If the mass of P is 0.45kg then what is the tension in the string?
Using mg – T = ma, and the known variables we can find that T = 3.6N
P Q

6. Given that T is 3.6N, what is the mass of Q?
Particles P and Q are attached to the ends of a light inextensible string which passes over a smooth pulley. The system is held at rest with the string taut and its straight parts vertical. Both particles are at a height of 0.36m above the floor. The system is released an P begins to fall, reaching the floor after 0.6s.
Given that T is 3.6N, what is the mass of Q?
Given that T – mg = ma describes the relationship of tension, acceleration and mass with regard to Q, we can solving for m being 0.3kg.
P Q

7. What is the velocity of Q when P hits the ground?
Particles P and Q are attached to the ends of a light inextensible string which passes over a smooth pulley. The system is held at rest with the string taut and its straight parts vertical. Both particles are at a height of 0.36m above the floor. The system is released an P begins to fall, reaching the floor after 0.6s.
What is the velocity of Q when P hits the ground?
Given that the time taken is 0.6s, acceleration is 2m/s and u is 0m/s, we can calculate v to be 1.2m/s
P Q

8. What is the maximum height that Q will reach?
Particles P and Q are attached to the ends of a light inextensible string which passes over a smooth pulley. The system is held at rest with the string taut and its straight parts vertical. Both particles are at a height of 0.36m above the floor. The system is released an P begins to fall, reaching the floor after 0.6s.
What is the maximum height that Q will reach?
Since P falls 0.36m, that means Q will move up to be 0.72m above the ground, but it will also have an upward velocity of 1.2m/s. With a=-10, v = 0, u = 1.2m/s, you can calculate s = 0.072m, for a total height of 0.792m.
P Q

9. What can you say for certain about the masses of P and Q?
Particles P and Q have masses m kg and (1 − m) kg respectively. The particles are attached to the ends of a light inextensible string which passes over a smooth fixed pulley. P is held at rest with the string taut and both straight parts of the string vertical. P and Q are each at a height of h above horizontal ground P is released and Q moves downwards and hits the ground and comes to rest. The velocity-time graph shows P while Q is moving downwards or is at rest on the ground.
What can you say for certain about the masses of P and Q?
Given that Q moves down it must have a mass greater than P, therefore if the mass of Q is (1 – m) it must be that m < 0.5kg.

10. Using the graph, describe the movement of P.
Particles P and Q have masses m kg and (1 − m) kg respectively. The particles are attached to the ends of a light inextensible string which passes over a smooth fixed pulley. P is held at rest with the string taut and both straight parts of the string vertical. P and Q are each at a height of h above horizontal ground P is released and Q moves downwards and hits the ground and comes to rest. The velocity-time graph shows P while Q is moving downwards or is at rest on the ground.
Using the graph, describe the movement of P.
P accelerates upwards until the velocity reaches 2m/s at 0.5s. At this point object continues to move upwards, but is decelerating. Eventually it reaches its maximum height before accelerating downwards and reaching a maximum velocity of 2m/s before being stopped by the taut string.

11. What is the initial height of P and Q?
Particles P and Q have masses m kg and (1 − m) kg respectively. The particles are attached to the ends of a light inextensible string which passes over a smooth fixed pulley. P is held at rest with the string taut and both straight parts of the string vertical. P and Q are each at a height of h above horizontal ground P is released and Q moves downwards and hits the ground and comes to rest. The velocity-time graph shows P while Q is moving downwards or is at rest on the ground.
What is the initial height of P and Q?
Using our description of the movement we can determine that at 0.5s the object Q hits the ground. Knowing this we can calculate the displacement by finding the area of the triangle to be 0.5, thus 0.5m.

12. Particles P and Q have masses m kg and (1 − m) kg respectively
Particles P and Q have masses m kg and (1 − m) kg respectively. The particles are attached to the ends of a light inextensible string which passes over a smooth fixed pulley. P is held at rest with the string taut and both straight parts of the string vertical. P and Q are each at a height of h above horizontal ground P is released and Q moves downwards and hits the ground and comes to rest. The velocity-time graph shows P while Q is moving downwards or is at rest on the ground.
What is the mass of P?
First, calculate the acceleration by finding the gradient of the first line to be 4 (a = 4m/s2). Second, set up the equations (1 – m)g – T = (1 – m)a, and T – mg = ma. Lastly, put in your known values and solve, finding the mass to be 0.3kg

13. What is the tension in the string as Q moves downward?
Particles P and Q have masses m kg and (1 − m) kg respectively. The particles are attached to the ends of a light inextensible string which passes over a smooth fixed pulley. P is held at rest with the string taut and both straight parts of the string vertical. P and Q are each at a height of h above horizontal ground P is released and Q moves downwards and hits the ground and comes to rest. The velocity-time graph shows P while Q is moving downwards or is at rest on the ground.
What is the tension in the string as Q moves downward?
Using the mass of 0.3 we can plug it into either of the equations to find that T is 4.2N

14. What is the acceleration of P after Q has reached the ground?
Particles P and Q have masses m kg and (1 − m) kg respectively. The particles are attached to the ends of a light inextensible string which passes over a smooth fixed pulley. P is held at rest with the string taut and both straight parts of the string vertical. P and Q are each at a height of h above horizontal ground P is released and Q moves downwards and hits the ground and comes to rest. The velocity-time graph shows P while Q is moving downwards or is at rest on the ground.
What is the acceleration of P after Q has reached the ground?
We know that after 0.5s that the object Q has reached the ground, and that there is slack in the string. Therefore, the only force acting on P is gravity.

15. How long will P keep moving after Q has reached the ground?
Particles P and Q have masses m kg and (1 − m) kg respectively. The particles are attached to the ends of a light inextensible string which passes over a smooth fixed pulley. P is held at rest with the string taut and both straight parts of the string vertical. P and Q are each at a height of h above horizontal ground P is released and Q moves downwards and hits the ground and comes to rest. The velocity-time graph shows P while Q is moving downwards or is at rest on the ground.
How long will P keep moving after Q has reached the ground?
Knowing that gradient of the line after 0.5s is -10, we can calculate the area under the right two triangles to each be 0.2, giving us a total of 0.4s.