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NCERT Solutions Curiosity Chapter 5 .7 Types of Motion — Activity 5.3: Let us explore

Book page 91 & 925 Updated on2026-09-05

Q1.
Take an eraser and drop it from a certain height. Observe its motion. Does it move along a straight line?
Answer

Yes. Once you let go, the eraser falls straight down along a vertical line until it hits the floor. Its path is a straight line, so this is linear motion.

When an object moves along a straight line,
its motion is called linear motion.

What to observe carefully: hold the eraser still, then simply open your fingers — do not throw it sideways. Watch the path from the side. It goes straight down, and it lands directly below the point from which it was released.

Why it falls straight: the Earth pulls every object straight down towards its centre. If nothing pushes the eraser sideways, there is no reason for it to drift left or right, so the path stays a straight vertical line. (Notice that the speed increases as it falls — but the type of motion is decided by the shape of the path, not by the speed.)
Try This: Drop the eraser and, at the same instant, throw a second eraser sideways from the same height. The dropped one moves in a straight line; the thrown one follows a curved path. Only the first is linear motion.
Q2.
When an orange drops from the tree, does it move in a straight line?
Answer

Yes. An orange that becomes ripe and separates from its stalk falls vertically downwards in a straight line, exactly like the eraser. It is another example of linear motion.

Two things to notice:

  • The orange lands almost directly below the branch it hung from — proof that the path was vertical.
  • It moves faster and faster as it comes down, but that does not change the type of motion. Linear motion only means the path is a straight line.
When it would not be a straight line: if a strong wind blows, or if a bird or a boy's stone knocks the orange sideways, it gets a sideways push as well as the downward pull, and the path curves. In still air, though, the fall is straight.
Did you know? A story of exactly this kind — an apple falling from a tree — is said to have set Isaac Newton thinking about why objects always fall towards the Earth.
Q3.
Have you seen the Republic Day parade? Recall the march-past of students during the parade. Do they move on a straight-line path?
Answer

Yes. During the march-past on Kartavya Path the contingents move in straight lines — that is the whole point of the drill. Each row keeps its line, each student keeps a fixed distance from the one in front, and the entire block slides forward along a straight path. This is linear motion.

Part of the paradePathType of motion
Students marching down the roadStraight lineLinear motion
The whole contingent turning a cornerCurved (an arc)Not linear
A marcher's arms swinging front and backTo and fro about the shoulderOscillatory motion
Wheels of the tableaux (jhankis)Round and roundCircular motion
Why the drill insists on it: a straight-line path is the only one on which every marcher in a row covers the same distance in the same time. On a curve, the marcher on the outside would have to walk further and the line would break. That is why contingents slow down and change step while turning.
Look for it: the same picture in the book shows a heavy box being pushed across the floor (Fig. 5.14) — another everyday case of linear motion.
Q4.
When an object moves along a straight line, its motion is called linear motion. Identify such linear motion in your surroundings.
Answer

Linear motion is everywhere once you start looking for a straight-line path.

Example around youWhy it is linear motion
A car or bus on a straight roadThe whole vehicle travels along a straight path
A lift going up or down its shaftVertical straight-line path between floors
A heavy box being pushed across the floorSlides straight in the direction of the push
An athlete running the 100 m raceStraight track from start to finish
A ball rolling down a straight rampPath is a straight slope
A drawer being pulled out of a tableMoves straight out along its rails
Rain falling on a still dayEach drop falls along a vertical straight line
A train on a straight stretch of trackRails keep it exactly on a straight path
A useful caution: a bicycle going straight down a road shows linear motion as a whole, but its wheels are in circular motion at the same time, and the pedals go round in circles too. One machine can show more than one type of motion at once — always say which part you are talking about.
Q5.
But do things always move along a straight line? You might have enjoyed playing on swings and merry-go-rounds. Are these types of motion also linear motion?
Answer

No. Neither of them is linear motion, because in neither case is the path a straight line.

RideShape of the pathType of motion
Merry-go-roundA complete circle, round and round the central poleCircular motion
SwingA short arc, forward and back over the same pathOscillatory motion

Notice the difference between the two. The merry-go-round keeps going the same way round and completes circle after circle. The swing comes back along the same arc — forward, back, forward, back — about a fixed lowest position.

Path is a straight line → linear motion
Path is a circle → circular motion
Path is to and fro about a fixed position → oscillatory motion
Why the type of motion matters: the name is decided entirely by the shape of the path, never by speed and never by what the object is. A slow car and a fast car on a straight road are both in linear motion; a slow fan and a fast fan are both in circular motion.
Tip: When you are unsure, trace the path with your finger in the air. If your finger comes back over the same short path, it is oscillatory. If it keeps going round, it is circular. If it goes straight on, it is linear.
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