NCERT Solutions for Class 9 Science Chapter 8 Motion in Hindi and English Medium for CBSE new session 2022-2023.

• ## Class 9 Science Chapter 8 Answers in English Medium

### NCERT Solutions for Class 9 Science Chapter 8

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 Class: 9 Science Chapter 8: Motion Content: Intext and Exercise Solutions Content Type: Text and Videos Format Medium: Hindi and English Medium
##### 9th Science Chapter 8 Answers in English & Hindi Medium

CBSE NCERT Solutions for Class 9 Science Chapter 8 Motion all Intext Questions with exercises questions answers free to download or use online. All the solutions are in updated form for current academic session. Download Class 9 Science App in Hindi and English Medium for offline use.

### Define speed and velocity. What are their SI units?

Speed: Speed of a body is defined as the distance travelled by the body in unit time.
Velocity: Velocity of a body is the distance travelled by the body in unit time in a given direction.
The SI unit is meter/second.

3 m/s ; zero

(a) 750 m ;
(b) 12.5 m.

(i) 1/15 m/s² ;
(ii) 3 km

10 seconds

### What type of motion of tips of second’s hand of a watch? Is it uniform or accelerated?

The motion of the tip of second’s hand of a watch is not a uniform motion. It is accelerated motion due to change in the direction of motion.

### What is the nature of the distance-time graph for uniform and non-uniform motion of an object?

When the motion is uniform, the distance-time graph is a straight line with some slope.
When the motion is non-uniform, the distance time graph is not a straight line. It can be any curve.

### What is locomotion?

Locomotion is the ability of an animal to move its whole body from place to place without any external forces.

### An athlete completes one round of circular track of diameter 200 m in 40 sec. What will be the distance covered and the displacement at the end of 2 minutes 20 sec?

Time taken = 2 min 20 sec = 140 sec. Radius, r = 100 m. In 40 sec the athlete complete one round. So, in 140 sec the athlete will complete = 140 ÷ 40 = 3.5 round. ⇒ Distance covered in 140 sec = 2πr × 3.5 = 2 × 22/7 × 100 × 3.5 = 2200 m. At the end of his motion, the athlete will be in the diametrically opposite position. ⇒ Displacement = diameter = 200 m.

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

(i) A body is said in uniform acceleration when its motion is along a straight line and its velocity changes by equal magnitude in equal interval of time.
(ii) A body is said in non-uniform acceleration when its motion is along a straight line and its velocity changes by unequal magnitude in equal interval of time.

Question 1:
A train travels 100 m long moving on a straight level track passes a pole in 5 s. Find (a) the speed of the train (b) the time it will take to cross a bridge 500m long.
(a) 20 m/s
(b) 30 s

Question 2:
A car accelerates uniformly from 18 km/h to 36 km h/ in 5 second. Calculate (i) the acceleration and (ii) the distance covered by the car in that time.
1 m/s² ; 37∙5 m                            