This post provides you a complete solution of Chapter 7 Motion Class 9 for Rajasthan Board of Secondary Education.
This post contains all the main and important topics which have complete and detailed description.
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Board |
RBSE |
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Subject |
Science |
|
Chapter |
Motion |
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No. of Intext questions |
20 |
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No. of End exercise questions |
10 |
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Prescribed Book |
NCERT Science |
Motion Questions- Answers
Intext Questions
Answers of Questions on Page 74
Q.1 An object has moved through a distance. Can it have zero displacement? If yes, support your answer with an example.
Answer
Yes, it can have zero displacement as for example, if a person throws a ball upwards
on a height ‘h’ and catch back it then the
Distance covered by the ball = h + h = 2h
Displacement of the ball = 0.
Q.2 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
second from his initial position?
Answer
If the farmer starts from point A, then at the end of 2 min. and 20 sec. (=2 × 60 + 20) = 140. He will reach the diagonally opposite corner C. The magnitude of
displacement of the farmer is
So, displacement of farmer at the end of 2 min 20 sec from his initial position is 14.14m.
Answers of Questions on Page 76
Q.1 Distinguish between speed and velocity.
Answer
Q.2 Under what condition is the magnitude of the average velocity of an object equals to its average speed?
Answer
When an object moves in one direction along a straight line.
Q.3 What does the odometer of an automobile measure?
Answer
Odometer of an automobile measure distance travelled by the automobile.
Q.4 What does the path of an object look like when it is in uniform motion?
Answer
Straight line path.
Q.5 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 ms-1.
Answer
Answers of Questions on Page 77
Q.1When will you say a body is in : (i) Uniform acceleration, (ii) Non-uniform acceleration?
Answer
(i) A body has uniform acceleration if its velocity changes by an equal amount in
equal intervals of time.
(ii) A body has non-uniform acceleration if its velocity changes by unequal amount in equal interval of time.
Q.2 A bus decreases its speed from 80 kmh-1 to 60 kmh1 in 5 s. Find acceleration of the bus.
Answer
Answer
Answers of Questions on Page 81
Q.1 What is the nature of the distance-time graphs for uniform and non-uniform motion of an object?
Answer
(i) For uniform motion distance-time graph is a straight line having constant gradient
or slope as shown in figure
(ii) For non-uniform motion, distance-time graphs is a curve having increasing gradient or slope or decreasing gradient as shown in figures.
Q.2 What can you say about the motion of an object whose distance-time graph is a straight line parallel to the time-axis?
Answer
It means the distance of the object is not changing with time. Thus, the object is stationary.
Q.3 What can you say about the motion of an object if its speed-time graph is a straight line parallel to the time axis?
Answer
The object has a uniform speed.
Q.4 What is the quantity which is measured by the area occupied below the velocity-time graph?
Ans.
Distance covered by the body in the given time interval.
OR
Magnitude of the displacement of a body.
Answers of Questions on Page 82-83
Q.1A bus starting from rest moves with a uniform acceleration of 0.1 ms-2 for 2 minutes.
Find: (a) the speed acquired, (b) distance travelled.
Q.2A train is travelling at a speed of 90 kmh-1. Brakes applied so as to produce a uniform acceleration of – 0.5 ms-1. Find how far the train will go before it is brought to rest?
Answer
Q.3 A trolley, while going down an inclined plane has an acceleration of 2 cms-2. What will be its velocity 3 s after the start?
Answer
Q.4 A racing car has a uniform acceleration of 4 ms-2. What distance will be cover in 10s after start?
Answer
Q.5 A stone is thrown in a vertically upward direction with a velocity of 5 ms-1. If the
acceleration of the stone during its motion is 10 ms-2 in the downward direction, what will be the height attained by the stone and how much time will it take to reach there.
Answer
Answers End Exercise Questions on Page 85-86
Q.1 An athlete completes on round of a circular track of diameter 200 m in 40 s. What will be the distance covered and the displacement at the end of 2 minutes and 20 second?
Answer
Q.2 Joseph jogs from one end A to the other end B of a straight 300 m road in 2 minutes 50 seconds and then turn around and jogs 100 m
back to point C in another 1 minute. What are Joseph’s average speed and
velocities in jogging (a) from A to B and (b) from A to C?
Answer
Q.3 Abdul, while driving to school, computes the average speed for his trip to be 20 kmh-1. On his return trip along the same route, there is less traffic and the average speed is 30 kmh-1. What is the average speed for Abdul’s trip?
Answer
Answer
Q.5 A driver of a car travelling at 52 kmh-1 applies the brakes and accelerates uniformly in the opposite direction. The car stops in 5s. Another driver going at 3
kmh-1 in another car applies his breaks slowly and stop in 10 s. On the same graph paper the speed versus time graph for the two cars. Which of the two cars travelled farther after the brakes were applied?
Answer
Q.6Figure shows the distance-time graph of three objects A, B and C. Study the graphs and answer the following questions:
Answer
(i) Which of the three is travelling the fastest.
(ii) Are all three ever meet at the same point on the road?
(iii) How far has C travelled when B passes A?
(iv) How far has B travelled by the time it passes C?
Answer
Q.7 A ball is gently dropped from a height of 20 m. If its velocity increases uniformly at the rate of 10 ms-2, with what velocity will it strike the ground? After what
time will it strike the ground?
Answer
Q.8 The speed-time graph for a car is shown in figure.
(a) Find how far the car travels in the first four 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?
Answer
Q.9 State which of the following situations are possible and give an example for each of these:
(a)An object with a constant acceleration but zero velocity.
(b)An object moving in a certain direction with an acceleration in the perpendicular direction.
Answer
(a) When an object is thrown vertically upwards, it velocity at the highest point is zero but it has constant acceleration = 9.8 ms-2.
(b) An object moving in a circular path with uniform speed its acceleration is always perpendicular to the direction of the motion of the object.
Q.10 An artificial satellite is moving in a circular orbit of radius 42,250 km. Calculate its speed if it takes 24 hours to revolve around the earth.
Answer
Related Topics
RBSE Class 9 Science All Chapters Solutions
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