(a) Define uniform circular motion. (b) Ram goes for a morning walk in a circular park daily. He com

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7. MOTION

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$(a)$ Define uniform circular motion.

$(b)$ Ram goes for a morning walk in a circular park daily. He completes one revolution of the park in $4$ minutes. Find his speed if the diameter of the park is $420\, m$.

$(c)$ Draw velocity$-$time graph for uniform motion along a straight line. How can you find distance covered by a body from this graph ?

Option A

Option B

Option C

Option D

Solution

$(a)$ A body is said to be in uniform circular motion, if it moves along a circular path with constant speed.

$(b)$ Given $t=4$ min $=4 \times 60=240 s , r=210 m$ $v=$

Total distance covered in one revolution

$S=2 \pi r=2 \times 22 / 7 \times 210=1320 m$

Therefore, speed $=$ distance $/$ time

$=1320 / 240=5.5 m s ^{-1}$

$(c)$ The graph is as shown

.Area under the velocity$-$time graph gives the distance covered by an object.

Standard 9

Science

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