📚 Learning Guide
Friction
hard

A skateboarder weighing 70 kg accelerates down a hill, reaching a speed of 10 m/s just before hitting the flat ground. If the coefficient of kinetic friction between the skateboard wheels and the ground is 0.3, calculate the distance over which the skateboarder will come to a stop after hitting the ground. (Assume no other forces are acting on the skateboarder besides friction.)

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Choose the Best Answer

A

Approximately 11.67 meters

B

Approximately 5.00 meters

C

Approximately 15.00 meters

D

Approximately 20.00 meters

Understanding the Answer

Let's break down why this is correct

Answer

The skateboarder has kinetic energy that is lost to friction, so the friction force \(f=\mu_k N\) is \(0. 3\times70\times9. 8\approx206\text{ N}\). That force gives a deceleration \(a=f/m=206/70\approx2. 94\text{ m/s}^2\).

Detailed Explanation

The friction force pulls back on the skateboarder and slows him at a constant rate of a = μg. Other options are incorrect because This option assumes the skateboard stops very quickly, as if friction were much larger; This answer treats friction as weaker than it really is.

Key Concepts

Energy Dissipation
Types of Friction
Coefficient of Friction
Topic

Friction

Difficulty

hard level question

Cognitive Level

understand

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