Question

16. An object of mass 100 kg is accelerateu WWIIY II
of 5 ms- to 8 m s-l in 6 s. Calculate the initial and final
momentum of the object. Also, find the magnitude of the force
exerted on the object.
17. Akhtar, Kiran and Rahul were riding in a motorcar that was
moving with a high velocity on an expressway when an insect
hit the windshield and got stuck on the windscreen. Akhtar
and Kiran started pondering over the situation. Kiran suggested
that the insect suffered a greater change in momentum as
compared to the change in momentum of the motorcar (because
the change in the velocity of the insect was much more than
that of the motorcar). Akhtar said that since the motorcar was
moving with a larger velocity, it exerted a larger force on the
insect. And as a result the insect died. Rahul while putting an
entirely new explanation said that both the motorcar and the
insect experienced the same force and a change in their
momentum. Comment on these suggestions.Answer for fun

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Answer 1

Answer:

16

According to question we have given,

m = 100 kg

u = 5 m/s

v = 8 m/s

t = 6 s

Initial moment = ?

Final momentum = ?

Force = ?

Now,

Initial momentum = m u

= 100 × 5

``

Final momentum = m v

= 100 × 8

``

Now,

Force required = Rate of change of momentum ÷ time taken

[Rate of change of momentum = final momentum - initial momentum]

= 800 - 500 ÷ 6

= 300 ÷ 6

=50 N

17.The suggestion made by Kiran that insect suffered a greater change in momentum as compared to the change in momentum of the care is wrong.

The suggestion made by Akhtar is also wrong . [ motorcar was moving with a larger velocity, it exerted a larger force on the insect. ]

The explanation given by Rahul is absolutely correct !

When the insect collided with the motor car , same force was experienced.

This is because action and reaction are always equal and opposite.

Changes in their respective momenta [ plural of momentum] is also the same.

As the change in momenta are in two direction , only their sign changes but magnitude is same  !

Answer 2

Ans 17$\huge{\underline{\underline{\boxed{\sf{\orange{Answer ࿐}}}}}}$

Rahul gave the correct reasoning and explanation that both the motorcar and the insect experienced the same force and a change in their momentum. As per the law of conservation of momentum.

When 2 bodies collide:

Initial momentum before collision

= Final momentum after collision

m1 u1+ m2 u2

= m1 v1+ m2 v2

The equal force is exerted on both the bodies but, because the mass of insect is very small it will suffer greater change in velocity.