Class 9 Physics Motion

Class 9 Physics Chapter Motion INTEXT Questions

Question 1: An object has moved through a distance. Can it have zero displacement? If yes, support your answer with an example.

Answer 1:

Yes, zero displacement is possible if an object has moved through a distance.

Suppose a body is moving in a circular path and starts moving from point A and it returns back at same point A after completing one revolution, then the distance will be equal to its circumference while displacement will be zero.

Question 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 seconds from his initial position?

Solution 2: Total time = 2 min 20 seconds

= 140 seconds

In 40 seconds , 1 round

Then in 140 seconds , number of rounds = 140/40 = 3.5 rounds

Question 3:

Which of the following is true for displacement?

• It cannot be zero.
• Its magnitude is greater than the distance travelled by the object.

Answer 3:

1. False, displacement can be zero and
2. Also false, because magnitude of displacement can never be greater than the distance travelled by the object. Question : Distinguish between speed and velocity.

Speed	Velocity
Speed is distance per unit time.	Velocity is displacement per unit time
In speed , the direction of motion of the body is not specified	In velocity , the direction of motion of the body is specified
Speed is a scalar quantity	Velocity is a vector quantity

Question 2: Under what condition(s) is the magnitude of average velocity of an object equal to its average speed?

Answer 2:The magnitude of average velocity of an object will be equal to its average speed in the condition of uniform velocity in a straight line motion

Question 3:

What does the odometer of an automobile measure?

Answer 3:

In automobiles, odometer is used to measure the distance.

Question 4:

What does the path of an object look like when it is in uniform motion?

Answer 4: An object has a uniform motion if it travels equal distance in equal intervals of time. Here speed is constant but direction may change.

In the case of uniform motion, the path of an object will look like a straight line path, a curved path, a circular path or even a zig-zag path

Question 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, 3×10^8 m/s.

Solution:   Speed = 𝑫𝒊𝒔𝒕𝒂𝒏𝒄𝒆 𝒕𝒓𝒂𝒗𝒆𝒍𝒍𝒆𝒅 / 𝒕𝒊𝒎𝒆 𝒕𝒂𝒌𝒆𝒏

Speed = 3×108 m/s Time = 5 min = 300 sec.

Distance travelled = speed × time taken

= 3×10^8 × 300

= 9×10^10   m

the distance of the spaceship from the ground station is 9×10^10 meters

Question 1:

When will you say a body is in (i) uniform acceleration? (ii) non-uniform acceleration?

Answer 1:

• A body is said in uniform acceleration if its velocity changes by equal amounts in equal intervals of time.
• A body is said in non-uniform acceleration if its velocity changes by unequal amounts in equal intervals of time.