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Problem 75 Easy Difficulty

Review Conceptual Example 16 as background for this problem. The water skier there has a mass of 73 kg. Find the magnitude of the net force acting on the skier when (a)she is accelerated from rest to a speed of 11 m/s in 8.0 s and (b) she lets go of the tow rope and glides to a halt in 21 s.

Answer

$1.0 \times 10^{2} \mathrm{N}$
$38 \mathrm{N}$

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Video Transcript

we begin disgrace from by calculating the acceleration and then a couple of the net force that acts on the skier. So to conflict acceleration, we have to use the following equation. The acceleration is equals to the variation in the velocity divided by the time it took. So in the first item we have 11 minus zero, divided by eight second show. Its acceleration is 11 divided by eight meters per second square. The Newton's second law tells us that the net force acting on the skier is it goes to its mass times acceleration. It's mast, it's 73 kilograms and declaration is 11 divided by eight. These results in a net force off approximately 100 Newtons for the first item on the second item. The acceleration is it close to the variation in the velocity. This time the velocity goes from 11 to 0. So the final velocities is muller than the initial velocity. Therefore, the variation that velocity is negative, so negative 11 divided by 21 seconds. So this is the acceleration in the situation. Now the net force that actually skier is equals to the mass times acceleration again and now it's equal stewed minus 73 times 11 divided by 21. And these results in the net force off approximately 38 minus 38 new terms. So the magnitude of the net force in the second situation is 38 neutrons.