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Page No 102: - Chapter 8 Motion class 9 ncert solutions Science - SaraNextGen [2024]


Question 1:

Distinguish between speed and velocity.

Answer:

Speed

Velocity

Speed is the distance travelled by an object in a given interval of time. It does not have any direction.

Velocity is the displacement of an object in a given interval of time. It has a unique direction.

Speed is given by the relation:

https://img-nm.mnimgs.com/img/study_content/curr/1/9/8/120/426/Chapter%208_html_m2ce89d4c.gif

Velocity is given by the relation:

https://img-nm.mnimgs.com/img/study_content/curr/1/9/8/120/426/Chapter%208_html_6cc76c76.gif

The speed of an object can never be negative. At the most, it can become zero. This is because distance travelled can never be negative.

The velocity of an object can be negative, positive, or equal to zero. This is because displacement can take any of these three values.

Question 2:

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

Answer:

https://img-nm.mnimgs.com/img/study_content/curr/1/9/8/120/431/Chapter%208_html_m61c9c0e2.gif

https://img-nm.mnimgs.com/img/study_content/curr/1/9/8/120/431/Chapter%208_html_5e9a5bc0.gif

If the total distance covered by an object is the same as its displacement, then its average speed would be equal to its average velocity.

 

 

Question 3:

What does the odometer of an automobile measure?

Answer:

The odometer of an automobile measures the distance covered by an automobile.

 

Question 4:

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

Answer:

An object having uniform motion has a straight line 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 × 108 m s−1.

Answer:

Time taken by the signal to reach the ground station from the spaceship

= 5 min = 5 × 60 = 300 s

Speed of the signal = 3 × 108 m/s

https://img-nm.mnimgs.com/img/study_content/curr/1/9/8/120/444/Chapter%208_html_3ab42551.gif

∴Distance travelled = Speed × Time taken = 3 × 108 × 300 = 9 × 1010 m

Hence, the distance of the spaceship from the ground station is 9 × 1010 m.

Also Read : Page-No-103:-Chapter-8-Motion-class-9-ncert-solutions-Science

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