CBSE Class 7 Science Types of Motion Worksheet Set 08

Answer: (c) random. Its path is irregular and keeps changing, which is random motion.

Teacher's Note:
1. Random motion has no fixed pattern.
2. The motion of a butterfly is also random.

Answer: (b) oscillatory. The swing moves to and fro about a mean position, which is oscillatory.

Teacher's Note:
1. Oscillatory motion repeats at regular intervals.
2. A pendulum shows the same motion.

Answer: (b) rectilinear. Motion along a straight line is rectilinear motion.

Teacher's Note:
1. Rectilinear motion is also called linear motion.
2. A falling stone also moves in a straight line.

Answer: (b) circular and periodic. The Earth follows a nearly circular path and repeats it every year.

Teacher's Note:
1. Its orbit is slightly elliptical.
2. Its spinning on its axis is rotational motion.

Answer: (b) The hands of a clock. The hands of a clock repeat their motion after fixed time intervals.

Teacher's Note:
1. Periodic motion repeats after equal intervals of time.
2. Not all periodic motion is to and fro.

Answer: (c) both rotational and rectilinear motion. The wheel spins about its axle and also moves forward along the road.

Teacher's Note:
1. A spinning top shows only rotational motion.
2. Many real motions are combinations.

Answer: A body is in motion when its position changes with time with respect to a fixed reference point. If the position does not change, the body is at rest.

Teacher's Note:
1. Motion is always described with respect to a reference point.
2. A fixed object such as a tree or building is often used.

Answer: Three types are rectilinear (straight line), circular and oscillatory motion. Rotational, periodic and random motion are other types.

Teacher's Note:
1. The type depends on the path followed.
2. A body may show more than one type at the same time.

Answer: The bullet moves along a nearly straight line, so it shows rectilinear motion. The path bends slightly because of gravity over a long distance.

Teacher's Note:
1. Rectilinear motion happens along a straight path.
2. We ignore the small curve for a short range.

Answer: A motion that repeats itself after equal intervals of time is called periodic motion. The Earth going round the Sun and the swinging of a pendulum are examples.

Teacher's Note:
1. The fixed interval is called the time period.
2. A pendulum clock depends on periodic motion.

Answer: (i) oscillatory; (ii) circular; (iii) rectilinear; (iv) rectilinear; (v) oscillatory (vibratory).

Teacher's Note:
1. Look at the path followed to decide the type.
2. Vibration is a quick oscillation about a mean position.

Answer: You are at rest with respect to the bus and other passengers. You are in motion with respect to the trees and buildings outside.

Teacher's Note:
1. Rest and motion are relative terms.
2. They depend on the chosen reference point.

Answer: The classroom is at rest with respect to the school building or the ground. With respect to the Sun it is in motion because the Earth is moving.

Teacher's Note:
1. Whether something is at rest depends on the observer's reference.
2. Everything on Earth moves with the Earth.

Answer: The hour hand moves along a circle and repeats its path every 12 hours. So it shows circular motion that is also periodic.

Teacher's Note:
1. The second hand has the same type of motion but is faster.
2. The tip of the hand moves on a circle.

Answer: The ball moves up and down about its mean position again and again. This is oscillatory (vibratory) motion.

Teacher's Note:
1. It repeats at equal time intervals.
2. The motion slowly dies down because of air resistance.

Answer: In rotational motion a body spins about a fixed axis passing through it. Examples are a spinning top and a ceiling fan.

Teacher's Note:
1. Every point of the body moves in a circle around the axis.
2. The axis may be inside the body.

Answer: The foot moves up and down repeatedly. This is oscillatory motion.

Teacher's Note:
1. It repeats at regular intervals.
2. The pedal turns the wheel, which shows rotational motion.

Answer: Rectilinear motion.

Teacher's Note:
1. The path is a straight line.
2. The wheels also rotate while the cycle moves forward.

Answer: Rotational motion of each wheel about its axle, along with rectilinear motion of the cart.

Teacher's Note:
1. The wheel spins and moves forward together.
2. This is a combined motion.

Answer: Rotational motion about its own axis.

Teacher's Note:
1. The top may also wobble slightly.
2. Its axis is a line through the top.

Answer: Rectilinear motion, along a vertical straight line.

Teacher's Note:
1. Its speed increases as it falls.
2. Gravity pulls it downwards.

Answer: Circular motion, which is also periodic.

Teacher's Note:
1. The child moves around a fixed centre.
2. The motion repeats after equal intervals.

Answer: Random motion, because the path keeps changing without a pattern.

Teacher's Note:
1. Random motion cannot be predicted.
2. Dust particles in air also show random motion.