Numerical Problems on Motion CBSE Class 9 Science

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Last Updated on September 1, 2024 by XAM CONTENT

Hello students, here you will find numerical problems on motion with answers. These numericals on Motion are very useful for students studying in CBSE Class 9 or for anyone who wants to practice some problems on these topics.

Before we start solving the numerical problems, let’s see some important points and formulae. This will help you to solve the problems efficiently.

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Table of Contents

Important Concept and Formulae

(1) Speed or velocity $=\frac{\text { distance }}{\text { time }}=\frac{S}{t}$ where $S$ is distance and $t$ is time
(2) Average speed, $v_{a v}=\frac{\text { Total distance }}{\text { Total time taken }}$
(3) Equations of Motion
(i) $\qquad$ $v=u+$ at or $v-u=a t$
or $\quad a=\frac{v-u}{t}$ or $t=\frac{v-u}{a}$
where $\quad v=$ final speed $u=$ initial speed
$a=$ acceleration and $t=$ time
(ii) $v^2-u^2=2 a S$ or $v^2=u^2+2 a S$
(iii) $\mathrm{S}=u t+1 / 2 a t^2$

(4) Angular speed, $\omega=\frac{\theta}{t}$, also $\omega=\frac{v}{r}$

Motion Numerical Problems with Answers

Problem 1:

A car travels 30 km at a uniform speed of 40 km/h and the next 30 km at a uniform speed of 20 km/h. Find its average speed.

Ans. 80/3 km/h

Problem 2:

On a 60 km track, a train travels the first 30 km at a uniform speed of 30 km/h. How fast must the train travel the next 30 km so as to average 40 km/h for the entire trip?

Ans. 60 km/h

Problem 3:

A train travels at 60 km/h for 0.52 hour, 30 km/h for the next 0.24 hour and then 70 km/h for the next 0.71 hour. What is the average speed of the trip?

Ans. 59.93 km/h

Problem 4:

A car travels a certain distance with a speed of 50 km/h and returns with speed of 40 km/h. Calculate the average speed after the whole journey.

Ans. 44.44 km/h

Problem 5:

The distance between the house and the school of a boy is 3.6 km. If he takes 6 minutes to reach his school by car, calculate his speed in m/s. Also express his speed in km/h.

Ans. 10 m/s

Problem 6:

A railway train 200 m long, passes over a bridge 800 m long. Find the time it takes to cross the bridge when it is moving with a uniform velocity of 36 km/h.

Ans. 100 s

Problem 7:

A body has an average speed of 30 m/s. If its final speed is 40 m/s, did the body start from rest or motion? If it started from motion what was its initial speed?

Ans. u = 20 m/s which is not zero, therefore, the body was initially not at rest.

Problem 8:

A trolley while going down an inclined plane has an acceleration of 2 m/s. What will be it velocity 3 s after the start?

Ans. 6 m/s

Problem 9:

Figure 2.15 shows the velocity-time graph of an object.
(a) Describe the motion of the object during 45 s.
(b) What is the total distance covered by the object?
(c) What is its acceleration during the first 10 s?
(d) What is the acceleration during the last 15 s?

Ans.

(a) During the first 10 s, the object moved with uniform acceleration. During the next 20 s, it moved with uniform velocity, whereas during the last 15 s, it moved with uniform retardation.
(b) Total distance travelled = 975 m
(c) Acceleration = 3 m/s²
(d) -2 m/s²

Problem 10:

A body moving with a speed of 36 km/h is brought to rest in 10 s. What is the negative acceleration and the distance travelled by the body before coming to rest?

Ans. 1 m/s², 50 m

Also check

Topics from which numericals may be asked

Motion—displacement, velocity.
Uniform and non-uniform motion along a straight line.
Average speed and Average velocity
Acceleration.
Distance-time and velocity-time graphs for uniform and uniformly accelerated motion.
Equations of motion by graphical method.
Elementary idea of uniform circular motion.

Numericals from the above topics may be asked.

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Frequently Asked Questions (FAQs) on Motion Class 9 CBSE

Q1: Can a body at rest be in motion?

A1: Yes, a body at rest with respect to one body may be in motion with respect to another.

Q2: What does the idea of the speed of a body convey?

A2: Speed tells us how fast the body is moving.

Q3: Displacement covered by a point object is always greater than distance covered by it. Do you agree?

A3: Displacement of a body is always less than or equal to the distance covered by the body.

Q4: What is the nature of the distance-time graph for uniform motion?

A4: A straight line

Q5: Explain the terms distance and displacement with suitable examples.

A5: The actual length of the path covered by a moving body irrespective of the direction in which the body travels, is called distance. It is a scalar quantity. The change in the position of a body in a particular or specified direction is called its displacement. It is a vector quantity.

Q6: Define motion. What do you mean by a moving body?

A6: Motion means a change of position of one body in relation to another. A body is said to be in motion i.e., a body is said to be moving when its position changes continuously with respect to a stationary body taken as a reference point.

Q7: What do you mean by uniform circular motion?

A7: When a body moves in a circular path with a uniform speed (constant speed), its motion is called uniform circular motion.

Q8: Can uniform linear motion be accelerated?

A8: No.