NCERT Class VII Science Solutions: Chapter 13-Motion and Time Part 1

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Question 1:

Classify the following as motion along a straight line, circular or oscillatory motion:

  1. Motion of your hands while running.

  2. Motion of a horse pulling a cart on a straight road.

  3. Motion of a child in a merry-go-round.

  4. Motion of a child on a see-saw.

  5. Motion of the hammer of an electric bell.

  6. Motion of a train on a straight bridge.

Answer:

  1. Motion of your hands while running – Oscillatory motion.

    This motion takes place when the restoring force acting on the body is directly proportional to its displacement from its equilibrium position.

    Image result for Oscillatory motion

    Oscillatory Motion

    Image result for Oscillatory motion

  2. Motion of a horse pulling a cart on a straight road – Straight line motion.

    Linear motion is a one dimensional motion along a straight line, and can therefore be described mathematically using only one spatial dimension.

As showing in images is a horse pulling a cart on a straight road

Horse Pulling a Cart on a Straight Road

As showing in images is a horse pulling a cart on a straight road

  1. Motion of a child in a merry-go-round – Circular motion.

    Circular motion is a movement of an object along the circumference of a circle or rotation along a circular path.

    This diagram shows Circular Motion

    Circular Motion

    This diagram shows Circular Motion

  2. Motion of a child on a see-saw – Oscillatory motion.

Image result for Motion of a child on a see-saw

Motion of a Child on a See-Saw

Image result for Motion of a child on a see-saw

Motion of the hammer of an electric bell – Oscillatory motion.

As showing in images is a hammer of an electric bell

Hammer of an Electric Bell

As showing in images is a hammer of an electric bell

Motion of a train on a straight bridge – Straight line motion.

As showing in images is a train on a straight bridge

Train on a Straight Bridge

As showing in images is a train on a straight bridge

Question 2:

Which of the following are not correct?

  1. The basic unit of time is second.

  2. Every object moves with a constant speed.

  3. Distances between two cities are measured in kilometers.

  4. The time period of a given pendulum is not constant.

  5. The speed of a train is expressed in .

Answer:

  1. The basic unit of time is second – Correct

  2. Every object moves with a constant speed - Not correct

  3. Distances between two cities are measured in kilometers – Correct

  4. The time period of a given pendulum is not constant - Not correct

  5. The speed of a train is expressed in - Not correct

Question 3:

A simple pendulum takes to complete . What is the time period of the pendulum?

Answer:

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