A professional diver of mass 60 kg performs a dive from a...

A professional diver of mass 60 kg performs a dive from a platform 10 m above the water surface. Find the magnitude of the average impact force experienced by him if the impact time is 1 s on collision with the water surface. Assume that the velocity of the diver just after entering the water surface is 4 m/s (g = 10 m/s^2). A. 240 N B. 600 N C. 300 N D. 60 N

Transcript

00:01 Okay, we're trying to find the average force exerted on the diver, given the impact time is one second.

00:07 So immediately we're thinking impulse, right? they ask for a force, they give us a time that makes you think impulse right off the bat.

00:18 So remember impulse is equal to a force times some change in time, right? impulse is also equal to the change in momentum.

00:42 In other words, the mass times the final velocity minus the initial velocity, right? so let's see if we can use that to solve for the force.

01:01 So in other words, if we can find the change in velocity at the right time, then we can figure this out.

01:08 So let's label a few velocity.

01:11 Velocities here.

01:13 Up here, when he jumps off, he has velocity v -0.

01:17 Right before he hits the water, v1, and when he hits the water, v2.

01:23 That's our four meters per second that they tell us.

01:28 Okay, so what velocities are we using here? well, we're going to use that the force exerted is equal to his mass times.

01:41 We're trying to find the force that is exerted by the water.

01:48 Right so the velocity we're looking for here is v2 minus v1 and then we divide that by the time over which this occurs which is one second so that makes it nice how are we going to find v1 because they give us v2 right four meters per second how do we find v1 well let's use we could use energy or kinematics i'm going to choose to use kinematics in case you don't know how to use energy.

02:25 Energy, for conservation of energy, you basically just write it down because it's pretty simple...

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