Question

A block of mass 2 kg is suspended from a string, is released from a height of 5m as shown in figure then what will be the impulse when string. Just becomes tight :-
(1) 2 N-s
(2) 0.2 N-s
(3) 20 N-s
4) 200 N-s
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Answer 1

Given in the question :-

Mass of the block = 5 kg.

v = 2m/sec.

Now Kinetic energy of the block is ,

(1/2) mv² .

Assume the new height of the block be h.

So the change in potential energy at the highest point is equal to Kinetic energy .

∴ mgh = (1/2)mv²

h = (1/2g) v²

h = 2² /(2× 10)

h = 1/5

h = 0.2 m

or h = 20 cm.

It will rise upto 20 cm.

Hope it Helps.

Answer 2

Answer: option 3

Explanation: as we know that impulse is change in momentum (delta p)

Also, impulse= F× delta t

Therefore, t can be calculated as √2h/g

Which is = √2×5/10 = 1 secon

Hence, we get impulse as

Impulse= 2×10×1 = 20 Ns