# science

A ball of mass 1 kg dropped from 9.8m height , strikes the ground and rebounds to a height of 4.9m .If the time of contact between ball and ground is 0.1s,then find impulse and average force acting on ball.

1. 👍 7
2. 👎 9
3. 👁 6,237
1. 26ns

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2. 👎 16
2. Velocity when it hits the ground
u = sqrt(2gH)
= sqrt(2 * 9.8 * 9.8)
= 9.8 sqrt(2) m/s

Velocity just after hitting the ground
v = sqrt(2gH)
= sqrt(2 * 9.8 * 4.9)
= 9.8 m/s

Impulse = change in momentum
= mass × change in velocity
= m * (v - u)
= 1kg * (9.8 - (-9.8*sqrt(2)) m/s
= 9.8 * (1 + sqrt(2)) kgm/s
= 9.8 * 1.414 kgm/s
= 13.8572 kgm/s

Average Force = Impulse / Time taken
= 13.8572 / 0.1
= 1.38 N

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2. 👎 119
3. Answer is wrong

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2. 👎 18
4. Answer is wrong..the correct answer is 23.89Ns, 238.9N

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2. 👎 13
5. Answer is wrong..

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2. 👎 7
6. It's a wrong answer
Correct answer is 23.52Ns,235.2N

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7. The answer given by kundan is almost correct.
But only at the last part where he solve:
9.8*(1+root2)= 9.8*(1+1.414)= 9.8*2.414=23.857
This is where he went wrong
Similarly we can fine force

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2. 👎 5
8. Thanks for correcting the mistake

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2. 👎 3
9. Why has -ve sign being used in front of initial velocity ??

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2. 👎 2
10. What is meaning if square root 2

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11. Actually the correct answer is 23.89Ns and force is 238.9 N but how ? The solution is yet not cleared

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12. ......Question asked by Kundan......
Some favourite answers :
(1) 13.85 by Jitin Sharma
~ Wrong
(2) Correction of Jitin by Sireesha
He forgot to do the sum of √2 + 1
~ Okay
~ But How the (9.8 × 2.414) = 23.857
~ Wrong
(3) Chitransh
Last step -----> [9.8 × 2.414] = 23.657 N-s

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13. This all answers are wrong the write answer is 23.52Ns 235.2.

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14. Still if uh multiply 9.8*2.414
It comes out to 23.657 and not 23.857
But the answer given here in my material is 23.857

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2. 👎 1
15. Correct answer is 23.89ns,238.9n

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16. If u assume gravity is 10 instead of 9.8 you will get 23.89.

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2. 👎 0

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