## Class 9 - Physics

#### Motion

MCQ
Q&A
Question:
The mass of an empty 40 litre petrol tank of a vehicle is 8.0 kg.What will be its mass when filled completely with a fuel of density 700$kg/m3$

[Ans. 36 kg]

Motion - Questions
1. Are motion and rest absolute or relative? Explain with an example.
2. A bus decreases its speed from 80 km/h to 60 km/h in 5 s. Find the acceleration of the bus.
3. A train is running at a speed of 72 km/h. It crosses a bridge of length half kilometer in 1 minute. Calculate the length of the train.
4.

Which of the following situation is impossible to have?
Scene I: Object moving to east with velocity (v) and acceleration is acting towards west.
Scene II: Object is moving with variable velocity but fixed acceleration.
Scene III: Object is moving with uniform velocity but non-uniform acceleration.
Scene IV: Object is moving with uniform speed but variable acceleration.

5. What is meant by scalars and vectors?
6. Which of the following is true for displacement?
(a) It cannot be zero.
(b) Its magnitude is greater than the distance travelled by the object.
7. When will you say a body is in (i) uniform acceleration? (ii) nonuniform acceleration?
8.

Fill in the blanks :
If the position of an object does not change with time, it is said to be at _____.

9.

During an experiment, a signal from a spaceship reached the ground station in five minutes. What was the distance of the spaceship from the ground station? The signal travels at the speed of light, that is, 3 × 108 m s–1.

10.

Consider the following two scenarios and tell in which case average speed is harmonic mean or arithmetic mean?

Case 1: A fellow travels from city A to city B. For the first hour, he drove at the constant speed of 20 km/hr. Then he (instantaneously) increased his speed and, for the next hour, kept it at 30 km per hour. Find the average speed of the motion.

Case 2: A fellow travels from city A to city B. The first half of the way, he drove at the constant speed of 20 km per hour. Then he (instantaneously) increased his speed and traveled the remaining distance at 30 km per hour. Find the average speed of the motion.

11. A cyclist cycles for t second at a speed of 3 m/s and then for the same time at a speed of 5 m/s along a straight road due north. What is the average speed of the cyclist?
12. What does the slope of distance-time graph indicate?
13.

A particle moves along the x axis from A to B. Which Of the following values of the initial and final coordinates, which results in a negative displacement?
(a) A = 4m, B = 6m
(b) A = −4m, B = −2m

(c) A = −4m, B = −8m
(d) A = −4m, B = 2m

14. What does the odometer of an automobile measure?
15. What is the average velocity over the “round trip” of an object that is thrown straight up from the ground and falls straight back down to the ground?
16.

What is the nature of the distance-time graphs for uniform and non-uniform motion of an
object?

17. A scalar quantity has ?
(a) magnitude only
(b) direction only
(c) both direction and magnitude
(d) none of these
18.

A driver of a car travelling at 52 km/h applies the brakes and accelerates uniformly in the opposite direction. The car stops in 5 s. Another driver going at 3 km/h in another car applies his brakes slowly and stops in 10 s. On the same graph paper, plot the speed versus time graphs for the two cars. Which of the two cars travelled farther after the brakes were applied?

19. What do you mean by a body in rest?
20. Distinguish between speed and velocity.
21. What does the path of an object look like when it is in uniform motion?
22.

A racing car has a uniform acceleration of 4 m s–2.
What distance will it cover in 10 s after start?

23.

The equation v = u + at gives information as
(a) velocity is a function of time.
(b) velocity is a function of position.
(c) Position is a function of time.
(d) Position is function of velocity and time.

24. What will be the initial velocity of an object under free fall?
25. Orbit of an artificial satellite at distance 42260 km from earth is circular. It completes one revolution around the earth in 24 hours. Calculate its linear speed.
26.

Fill in the blanks :
The rate of change of velocity of a moving body with time is called ______.

27.

A car travels along a straight line and covers one third of total distance with speed of 4 m/s. The remaining distance, it covers with a speed of 2 m/s half the time and with speed of 6m/s for the other half time. Find the average speed of the car.

28. Mathematically prove that the distance (S) travelled by an object is the average mean of initial velocity(u) and final velocity(v) having constant acceleration(a) in the direction of motion in a straight line.
29.

An object has moved through a distance. Can it have zero displacement? If yes, support your answer with an example.

30.

Fig (below) shows the distance-time graph of three objects A,B and C. Study the graph and answer the following questions:

(a) Which of the three is travelling the fastest?
(b) Are all three ever at the same point on the road?
(c) How far has C travelled when B passes A?
(d) How far has B travelled by the time it passes C?

31.

A farmer moves along the boundary of a square field of side 10 m in 40 s. What will be the magnitude of displacement of the farmer at the end of 2 minutes 20 seconds?

32.

The equation S = ut + ½at2 gives information as
(a) velocity is a function of time.
(b) velocity is a function of position.
(c) Position is a function of time.
(d) Position is function of velocity and time.

33.

A train is travelling at a speed of 90 kmh–1. Brakes are applied so as to produce a uniform acceleration of – 0.5 ms–2. Find how far the train will go before it is brought to rest.

34.

The speed-time graph for a car is shown is figure below.

(a) Find how far does the car travel in the first 4 seconds. Shade the area on the graph that represents the distance travelled by the car during the period.

(b) Which part of the graph represents uniform motion of the car?

35. A trolley, while going down an inclined plane, has an acceleration of 2 cm s–2. What will be its velocity 3 s after the start?
36. Under what condition(s) is the magnitude of average velocity of an object equal to its average speed?
37. A train starting from a railway station and moving with uniform acceleration attains a speed 40 km/h in 10 minutes. Find its acceleration.
38.

A bus starting from rest moves with a uniform acceleration of 0.1 ms–2 for 2 minutes.
Find (a) the speed acquired, (b) the distance travelled.

39. What is the acceleration of a body moving with uniform velocity ?
40. What is SI unit of speed ? Is it same for velocity ?
41. A body is moving uniformly with a velocity of 5 m/s. Find graphically the distance travelled by it in 5 s.
42. What is the SI unit of acceleration ?
43. A solid of density 5000 $Kg/m3$ weighs 0.5 kg f in air.It is completely immersed in water of density 1000 $Kg/m3$.
(a) Calculate the apparent weight of the solid in water.
(b) What will be its apparent weight if water is replaced by a liquid of density 8000 $Kg/m3$ ?
44. A solid body of mass $4.0x103$ kg and volume $2 m3$ is put in water.Will the body float or sink ?
45. A stone tied to one end of a string is rotated in a circle.Explain what happens when the stone is released.
46. Can displacement and distance ever be equal ?
47. Define speed and velocity.What are their SI units ?
48. What is relative density ? What is its unit ?
49. What is meant by buoyant force ? Describe an experiment to demonstrate the existence of this force.
50. In the above question,calculate
(i) distance travelled from O to A.
(ii) distance travelled from B to C.
(iii) total distance travelled by the body in 16 sec.
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