Page 18 - 1202 Question Bank Physics Form 4

5. C When an object is rotated at a certain uniform speed, though the 21. D Both R and S are heavy objects and they will travel with same
speed is uniform, the direction of motion of the object keeps variation of velocity with time.
changing. Hence, acceleration is acting on the object.
22. D This is a non-free fall motion because of the effect of air
6. B s = (u + v)t resistance and parachute action on the parachutist. Hence,
1
2 velocity, acceleration and momentum are not constant.
1.5 = (0 + 20)t
1
2
t = 0.15 s 23. D Objects of different masses fall with the same acceleration if air
resistance does not exist (vacuum cylinder). Hence, they will
2
7. B v = u + 2as reach the floor at the same time.
2
35 = 0 + 2(4)s,
2
s = 153.1 m 24. D Apples of different masses fall with the same acceleration under
free fall condition (vacuum means no air resistance). Answer C
Hence, minimum runway is 154 m long
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not correct because no measurement was made.
8. B v = 600 m
5 × 5 s 25. A Inertia is the tendency of an object to remain at rest or, if
= 24 m s moving, to continue its motion in a straight line at uniform
–1
(6 drops of oil = 5 time intervals only) velocity. The concept of inertia is explained in Newton’s First
Law of Motion.
Total displacement
9. A Average velocity = Total time taken 26. A The larger the mass of an object, the larger the inertia of the
= 10 object.
20
= 0.5 m s –1 27. A The loaded supertanker is massive and has huge amount of
inertia. Hence, it’s very difficult to change the states of motion.
10. D Displacement measures the shortest distance travelled between
the starting point and the ending point. 28. D Inertia is the resistance of an object to change its state of motion.
Inertia is non-physical quantity. Mass is a measure of inertia.
11. C The gradient at PQ is increasing with time, hence the object’s
acceleration is increasing. The gradient at ST is zero, hence it’s 29. C There may be external forces acting on the object but they are
moving with uniform velocity. well balanced. Due to F = ma, a = 0 (uniform velocity) when
∑F = 0.
12. B Area of trapezium = (20 + 8)v = 56
1
2 30. C Newton’s Third Law of Motion states that for every force there
v = 112 is an opposite and equivalent force against it.
28
= 4.0 m s –1
31. B Objects with larger momentum are more difficult to stop.
13. B The acceleration of cyclists is positive in the beginning then zero 32. D When two or more objects act on each other, their total Chapter 2
and finally negative. momentum remains constant, provided there are no external
forces acting on the system.
14. B A steady speed means that the speed of the toy car remains the
same during the motion. 33. C m v + m v = m u + m u
1 1
2 2
2 2
1 1
15. B The gradient of the graph from Q to S is increasing and then 10 v + 0.1 × (–0.05) = 0

decreasing. (You may draw tangents along the curve Q to S to 1 000 v = 0.5 m s –1
confirm this)
1
AB
16. B s = ut + gt 2 34. C If body A exerts a force F on body B, then body B will exert an
equal and opposite force F on body A.
2 BA
1
= 0 + (9.81)(2.12) 2 35. D All the statements regarding action and reaction forces are true.
2
= 22.05 m
36. C Momentum, p = mv, v can be increased by increasing p.
17. D No air on the surface of the Moon. Objects of different masses
fall with the same acceleration if air resistance does not exist. 37. A m v + m v = m u + m u
2 2
1 1
2 2
1 1
Hence, they will reach the floor at the same time. (1 000 × 5.0) + (800 × 2.0) = (1 000 × 3.4) + 800v
v = 4 m s –1
18. C Gravitational acceleration is constant near the surface of the
Earth. 38. C Most of the weight of the rocket is the weight of the propellants.
In order to lighten the weight of the vehicle to achieve higher
1
19. C s = ut + gt acceleration, most launchers discard a portion of the vehicle in
2
2
1
0 + (9.81)t = 125 m a process called staging.
2
2
t = 5.05 s 39. D Recall the definition of acceleration. It’s the rate change of
velocity.
20. A By using v = u – 2gs
2
At maximum height, v = 0 40. C Force will not change the inertia of an object
Hence, s = u 2 v – u
2g 41. C a = t
s = 25 2 30
2 × 9.81 = 5
s = 31.9 m = 6 m s –2
F = ma
= 1 200 × 6
= 7 200 N
109
Answer QBank Physics F4.indd 109 10/02/2022 4:03 PM