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Class 9

Explore popular questions from Force and Law of Motion for Class 9. This collection covers Force and Law of Motion previous year Class 9 questions hand picked by experienced teachers.

Force and Law of Motion

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Q 1. A shell of mass 0.020 kg is fired by a gun of mass 100 kg If the muzzle speed of the shell is 80 m/s, the recoil speed of the gun -

A

14 m/s

B

0.012 m/s

0.016 m/s

D

100 m/s

Explanation

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Q 2. Two billiard balls each of mass 0.05 kg moving in opposite directions with speed 6 m/s collide and rebound with the same speed The magnitude of impulse imparted to each ball due to the other -

0.6 kg m/s

B

zero

C

6 kg m/s

D

none of these

Explanation

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Q 3. Assertion: Large force is required to move a body uniformly along a straight path
Reason: A body moving with uniform acceleration has a constant force acting on it

A

Both Assertion and Reason are true and Reason is the correct explanation of 'Assertion'

Both Assertion and Reason are true and Reason is not the correct explanation of 'Assertion'

C

Assertion is true but Reason is false

D

Assertion is false but Reason is true

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Q 4. Which of the following statements is/are not correct ?

A force is needed to keep a particle moving along a straight line with uniform velocity

B

The same force for the same time causes the same change in momentum for different bodies

C

Frictional force opposes both motion as well as relative motion

D

It is not motion, but relative motion that the frictional force opposes

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Q 5. A force of 50 dynes is acted on a body of mass 5g which is at rest for an interval of 3sec. The impulse is

A

{tex}{0.15}\times{10^{-3 }}{/tex}Ns

B

{tex}{0.98}\times{10^{-3 }}{/tex}Ns

{tex}{1.5}\times{10^{-3 }}{/tex}Ns

D

{tex}{2.5}\times{10^{-3 }}{/tex}

Explanation