1. 1 Higher Still Multiple Choice Mechanics: Forces

2. 2 Which of the following forces is required to lift a mass of 5 kg vertically upwards near the surface of the Earth at a constant speed of 4ms -1 ? A.5 N B.20 N C.40 N D.50 N E.200 N

3. 3 A parachutist of mass 50 kg descends towards the Earth at a constant velocity of 2 m s -1. The upward force acting on the parachutist is A.10 N B.25 N C.100 N D.200 N E.500 N

4. 4 A block of weight 1500 N is dragged along a horizontal road at constant speed by a force of 500N. What is the force of friction between the block and the road? A.3 N B.500 N C.1000 N D.1500 N E.2000 N

5. 5 Force is applied to an object of mass 2 kg, initially at rest on a friction-free horizontal surface, as shown in the following force- time graph. After 1 second, the speed of the object, in ms -1, is A.7.5 B.12.5 C.15 D.25 E.30

6. 6 A hot air balloon of mass 300 kg has people with a total mass of 250 kg on board. It floats at a steady height. The upthrust on the balloon is A.0 N B.500 N C.2500 N D.3000 N E.E 5500 N

7. 7 A rocket of mass 1200 kg rises vertically from a planet which has a gravitational field strength of 20 N kg -1. The rocket accelerates away from the surface of the planet at 2 ms -2. What force must the rocket motors produce to give this acceleration? A.12 000 N B.14 400 N C.24 000 N D.26 400 N E.48 000 N

8. 8 A block X of mass 3 kg is accelerated from rest by a force of 5 N for 2 s. An identical block Y is accelerated from rest by a force of 5 N for 4s. The ratio of kinetic energy of X to kinetic energy of Y after acceleration is A.5 : 3 B.3 : 4 C.2 : 1 D.1 : 2 E.1 : 4

9. 9 A horizontal force of 40 N is applied to two wooden blocks of masses 6 kg and 14 kg which are in contact with each other on a frictionless horizontal surface as shown. What is the size of the horizontal force acting on the 7 kg block? A.40 N B.28 N C.20 N D.16 N E.12 N

10. 10 Two blocks, X and Y, move along a frictionless horizontal surface at a constant velocity of 3ms -1. The force which X exerts on Y is A.0 N B.1 N C.3 N D.6 N E.9 N

11. 11 A horizontal force of 10 N is applied as shown to two blocks on a frictionless horizontal surface. What force does Y exert on X? A.0 N B.4 N C.5 N D.6 N E.10 N

12. 12 Two trolleys are joined together by a thread and are pulled by a horizontal force of 12 N along a level track as shown. One second after starting from rest, the thread breaks at X. Neglecting possible effects of friction, which statements correctly describe the motion of both trolleys after the thread breaks. Trolley A Trolley B A.constant velocity of 8ms -1 constant velocity of 4ms -1 B.uniform acceleration of 4ms -2 uniform acceleration of 4ms -2 C.uniform acceleration of 12ms -2 constant velocity of 4ms -1 D.uniform acceleration of 12ms -2 comes to rest E.comes to rest comes to rest

13. 13 A lift is raised and lowered by means of a cable. In which of the following situations is the tension in the cable greatest? A.The lift is travelling upwards at constant speed. B.The lift is travelling downwards at constant speed. C.The lift is decelerating on the way down. D.The lift is accelerating on the way down. E.The lift is decelerating on the way up.

14. 14 An object of mass 1.0 kg hangs from a spring balance which is suspended on the inside of a lift. The balance reading is 10 N when the lift is stationary. What is the reading on the balance when the lift is accelerating upwards at 2 m s –2 ? (Use g=10 m s –2 ) A.2 N B.8 N C.10 N D.12 N E.30 N

15. 15 A mass of 0.060 kg is suspended from a spring balance inside a lift. The lift accelerates downwards at 4ms –2. What is the reading on the spring balance during this acceleration? (Use g=10 m s –2 ). A.0.24 N B.0.36 N C.0.60 N D.0.84 N E.2.4 N

16. 16 A woman is standing in a lift which is initially at rest. F is the force which is exerted by the woman’s feet on the floor of the lift, and R is the force exerted by the floor of the lift on the woman’s feet. If the lift begins to accelerate upwards, what changes, if any, take place in the magnitudes of F and R? A.F remains the same; R remains the same. B.F increases; R remains the same. C.F remains the same; R increases. D.F remains the same; R decreases. E.F increases; R increases.

17. 17 A man is standing in a lift which is initially at rest. F is the force which is exerted by the man’s feet on the floor of the lift, and R is the force exerted by the floor of the lift on the man’s feet. The lift is initially travelling upwards with a constant velocity. It then decelerates. When the deceleration starts what changes, if any, occur in F and R? A.F remains the same and R remains the same. B.F remains the same and R decreases. C.F remains the same and R increases. D.F decreases and R decreases. E.F decreases and R remains the same.

18. 18 A woman weighs 800 N and stands on an accurate weighing-machine in a lift. The reading on this weighing-machine is 820 N. This indicates that the lift is A.stationary B.moving upwards at a steady speed. C.moving downwards at a steady speed. D.accelerating upwards. E.accelerating downwards.

19. 19 A mass of 1.0 kg hangs from a spring balance which is suspended on the inside of a small rocket. What will the balance read when the rocket is accelerating upwards from the Earth's surface at a constant rate of 2.0 m s –2 ? (Use g= 10 m s –2 ). A.0 N B.2 N C.8 N D.10 N E.12 N

20. 20 Two masses are joined together by string Y and then hung from a beam using string X. String X is burned through using a candle. Neglecting the mass of each string, what is the tension in string Y I Before string X is burned through & II After string X is burned through? I Before II After A.40 N 40 N B.50 N 0 N C.60 N 40 N D.50 N 60 N E.40 N 0 N

21. 21 Two balls, of masses 1kg and 3kg, joined by a light string as shown, are falling freely. Assuming no air resistance, what is the tension in the string? A.0 N B.2 N C.4 N D.10 N E.20 N

22. 22 A tension force of 180 N is applied vertically upwards to a box of mass 15 kg. Assuming that the acceleration due to gravity is 10 m s –2 the acceleration of the box is A.2 m s –2 B.8 m s –2 C.10 m s –2 D.12 m s –2 E.20 m s –2