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.

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  1. 26ns

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  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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  3. Answer is wrong

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

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  5. Answer is wrong..

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  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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  8. Thanks for correcting the mistake

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

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  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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  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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