A ball weighing 200 g falls from a height of 20 m without initial velocity. Before hitting the ground, the speed of the ball
| November 25, 2020 | education
A ball weighing 200 g falls from a height of 20 m without initial velocity. Before hitting the ground, the speed of the ball is 18 m / s. What is the work of gravity? What is the change in the kinetic energy of the ball? What is the work of air resistance? What is the modulus of the average force of air resistance?
mgh = mv0 ^ 2/2 + Qt => Qt = mgh-mv0 ^ 2/2 = 7.6 Joule And its average resistance force is F = Qt / h = 0.38 N, but this is not average, because the average will be F + 0 / 2, because it increased linearly, so it will be equal to 0.19 Newton. The change in the kinetic energy of the ball is equal to mv0 ^ 2/2. Substitute. A (gravity) = mgh = 40 Newton.
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