Chapter 13: Motion and time

  Science

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  Chapter 13: Motion and time

  Class VII

  NCERT Questions

Question 1

Classify the following as motion along a straight line, circular or oscillatory motion: (i) Motion of your hands while running. (ii) Motion of a horse pulling a cart on a straight road. (iii) Motion of a child in a merry-go-round. (iv) Motion of a child on a see-saw. (v) Motion of the hammer of an electric bell. (vi) Motion of a train on a straight bridge. 

Answer 1

(i) Motion of your hands while running – Oscillatory motion.  (ii) Motion of a horse pulling a cart on a straight road – Straight line motion. (iii) Motion of a child in a merry-go-round – Circular motion. (iv) Motion of a child on a see-saw – Oscillatory motion. (v) Motion of the hammer of an electric bell – Oscillatory motion. (vi) Motion of a train on a straight bridge – Straight line motion.

Question 2

Which of the following are not correct? (i) The basic unit of time is second. (ii) Every object moves with a constant speed. (iii) Distances between two cities are measured in kilometers. (iv) The time period of a given pendulum is not constant. (v) The speed of a train is expressed in m/h. 

Answer 2

(i) The basic unit of time is second - Correct  (ii) Every object moves with a constant speed - Not correct  (iii) Distances between two cities are measured in kilometers - Correct (iv) The time period of a given pendulum is not constant - Not correct (v) The speed of a train is expressed in m/h - Not correct

Question 3

A simple pendulum takes 32 s to complete 20 oscillations. What is the time period of the pendulum?

Answer 3

The time taken to complete one oscillation is known as time period of the pendulum.