Page 117 - Ripples SCIENCE 7 - TEJPUR Edition 2024 Answer Key

5. Convert 54 km/h into m/s.

Ans: 54 km/h ⇒ m/5.
So, we will multiply it by 5/18.

54 x 5 = 3 x 5 = 15 m/s.
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6. What is a simple pendulum?
Ans: A simple pendulum is a metal ball, called bob, hanging from a string or a thread that
swings back & forth.

7. Define motion.

Ans: An object is said to be in motion when it changes its position over time with respect
to stationary objects around it.
8. Name an ancient device that was used to tell time.

Ans: Sundial indicated the time of the day by the position of the shadow of the object

exposed to the Sun's rays.
B. Short-answer questions.
1. Train A travelled a distance of 120 km in 3 hours whereas another train B travelled a

distance of 180 km in 4 hours. Which train travelled faster?

Ans: Given - Distance covered by train A = 120 km
Distance covered by train B = 180 km
Time taken by train A = 3 hours

Time taken by train B = 4 hours.

Speed of train A = Distance covered
Time taken

= 120
3
= 40 km/h

Similarly,
Speed of train B = 180
4

= 45 km/h

Since the speed of train B is greater, therefore train B travelled faster.
2. What is the difference between an odometer and a speedometer?

Ans: Speedometer and Odometer
The device which records speed of vehicles in km/h is called a speedometer. The

device which records the distance covered by a vehicle is called an odometer. An
odometer records the distance travelled by a vehicle in kilometres (km). We can

see a small rectangular window within the speedometer dial with the symbol `km’

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