A particle is moving in a circular path of radius r. The displacement after half a circle would be:
(a) Zero
(b) π r
(c) 2 r
(d) 2π r
Soln:
The answer is (c) 2 r.
Explanation:
After half revolution
Distance travelled = X circumference= πr
Path length
Displacement = Final position- Initial Position
It comes out to be the diameter of the circle = 2 r.
2. A body is thrown vertically upward with velocity u, the greatest height h to which it will rise is,
(a) u/g
(b) u2/2g
(c) u2/g
(d) u/2g
Soln:
The answer is (b) u2/2g.
Explanation:
V2= u2+2 as
here v = 0
a = -g
s = H
0 = u² -2gH
H = u²/2g
3. The numerical ratio of displacement to the distance for a moving object is
(a) always less than 1
(b) always equal to 1
(c) always more than 1
(d) equal or less than 1
Soln:
The answer is (d) equal or less than 1
Explanation:
The shortest distance between the initial and the endpoint is called displacement. Distance is the total path length.
Displacement is vector, and it may be positive or negative, whereas Distance is scalar, and it can never be negative.
The distance can be equal to or greater than displacement, which means the ratio of displacement to distance is always equal to or less than 1.
4. If the displacement of an object is proportional to square of time, then the object moves with
(a) uniform velocity
(b) uniform acceleration
(c) increasing acceleration
(d) decreasing acceleration
Soln:
The answer is (b) uniform acceleration
Explanation:
Velocity is measured in distance/second, and acceleration is measured in distance second2. Hence uniform acceleration is the right answer.
5. From the given v – t graph (Fig. 8.1), it can be inferred that the object is
(a) in uniform motion
(b) at rest
(c) in non-uniform motion
(d) moving with uniform acceleration
Soln:
The answer is (a) in uniform motion
Explanation:
From the above-given graph, it is clear that the velocity of the object remains constant throughout hence the object is in uniform motion.
6. Suppose a boy is enjoying a ride on a merry-go-round which is moving at a constant speed of 10 m/s. It implies that the boy is
(a) at rest
(b) moving with no acceleration
(c) in accelerated motion
(d) moving with uniform velocity
Soln:
The answer is (c) in accelerated motion
Explanation:
The boy is moving in a circular motion, and circular motion is an accelerated motion; hence C) is the right answer.
7. Area under a v – t graph represents a physical quantity which has the unit
(a) m2
(b) m
(c) m3
(d) m s–1
Soln:
The answer is (b) m
Explanation:
The area given in the graph represents Displacement, and its unit is meter. Hence, the answer is (b) m.
8. Four cars, A, B, C and D, are moving on a levelled road. Their distance versus time graphs are shown in Fig. 8.2. Choose the correct statement
(a) Car A is faster than car D.
(b) Car B is the slowest.
(c) Car D is faster than car C.
(d) Car C is the slowest.
Soln:
The answer is (b) Car B is the slowest.
Explanation:
The graph shows that Car B covers less distance in a given time than A, C and D cars hence it is the slowest.
9. Which of the following figures (Fig. 8.3) represents the uniform motion of a moving object correctly?
Soln:
The answer is (a)
Explanation:
Distance in graph a) is uniformly increasing with time hence it represents uniform motion.
10. Slope of a velocity–time graph gives
(a) the distance
(b) the displacement
(c) the acceleration
(d) the speed
Soln:
The answer is (c) the acceleration
11. In which of the following cases of motions the distance moved and the magnitude of displacement are equal?
(a) If the car is moving on a straight road
(b) If the car is moving in a circular path
(c) The pendulum is moving to and fro
(d) The earth is revolving around the Sun
Soln:
The answer is (a) If the car is moving on a straight road
Explanation:
In other cases given here, displacement can be less than distance; hence option (a) If the car is moving on a straight road, is the right answer.
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