Measurement of Length and Motion MCQs for UPSC Prelims
116 practice questions covering Measurement of Length and Motion, organised into 1 topics.
116 questions include a written explanation.
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Why is it useful to estimate a length before measuring it?
AAn estimate is always more accurate than a measurement
BEstimating tells you what material the object is made of
CEstimating removes the need to measure at all
DA measured value far from the estimate warns you that something has gone wrong
Show answer and explanation
Correct answer: D - A measured value far from the estimate warns you that something has gone wrong
An estimate sets a rough expectation, so a measurement far away from it points to a mistake such as a misread scale. Estimating does not replace measuring, and it is less accurate, not more. It says nothing about what an object is made of.
Q2
medium
Which of these units gives the same answer no matter who does the measuring?
AMetre
BHandspan
CCubit
DFootstep
Show answer and explanation
Correct answer: A - Metre
The metre is a standard unit fixed by agreement, so it is the same length for everyone. A handspan, a cubit and a footstep all depend on the size of the person's body, so each of them changes from person to person.
Q3
easy
How many centimetres make up $1\ \text{m}$?
A$60\ \text{cm}$
B$100\ \text{cm}$
C$1000\ \text{cm}$
D$10\ \text{cm}$
Show answer and explanation
Correct answer: B - $100\ \text{cm}$
One metre is divided into $100$ equal centimetres. $10$ is the number of millimetres in one centimetre. $1000\ \text{cm}$ would be $10\ \text{m}$. The number $60$ belongs to time, not to length.
Q4
medium
In circular motion, which of these stays the same?
AThe position of the object
BThe distance of the object from the centre
CThe direction in which the object is moving
DThe length of the path already covered
Show answer and explanation
Correct answer: B - The distance of the object from the centre
An object in circular motion keeps a fixed distance from the centre, which is what makes the path a circle. Its direction of travel keeps turning. Its position keeps changing, which is why it is in motion. The path already covered keeps growing.
Q5
easy
To measure a curved line with a thread, what is the correct order of steps?
ACut the thread into small pieces and count how many there are
BWrap the thread around the ruler and count the number of turns
CStraighten the thread on a ruler first, then lay it along the curve
DLay the thread along the curve, mark the two ends, then straighten the thread on a ruler
Show answer and explanation
Correct answer: D - Lay the thread along the curve, mark the two ends, then straighten the thread on a ruler
The thread must first take the shape of the curve, and the marked length is then pulled straight against a ruler and read. Straightening it first makes it impossible to match the curve. Cutting it into pieces loses the total length. Winding it round a ruler measures the ruler.
Q6
medium
A curved line drawn on paper is measured by laying a thread along it and then straightening the thread against a ruler. Why must the thread be laid along the curve without stretching it?
AA stretched thread stays stretched on the ruler, so the length read comes out too large
BA stretched thread springs back when it is released, so the length read on the ruler comes out too small
CStretching the thread changes the shape of the curve
DStretching the thread makes it harder to read on a ruler
Show answer and explanation
Correct answer: B - A stretched thread springs back when it is released, so the length read on the ruler comes out too small
A thread pulled tight is longer than its relaxed length, so less of it is needed to cover the curve. Once it is released and laid along the ruler it shrinks back, and the reading comes out too small. That is why the thread is laid gently along the curve. A curve drawn on paper does not change shape because a thread lies on it, and a stretched thread is no harder to read on a ruler.
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