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The graph shows the friction on a block against the push applied to it.

Try it on paper first. A hint, the key idea and the worked solution are here when you need them.

The graph shows the friction on a block against the push applied to it. The block has a mass of $2.5\ \text{kg}$ and rests on a level floor. Taking $g = 9.8\ \text{m/s}^2$ , find the coefficients of static and kinetic friction.

A graph of the friction force against the applied force. A blue straight line rises at 45 degrees from the origin to 10 newtons at an applied force of 10 newtons, which is the largest static friction. At that point the friction force drops to 7 newtons, and an orange horizontal line at 7 newtons continues to the right, for kinetic friction while the block slides.

Need a reminder? The key ideaShow

Static friction matches the push, up to a limit $f_{s,\max} = \mu_s N$ . Once the body slides, kinetic friction is $f_k = \mu_k N$ , nearly steady, with $\mu_k < \mu_s$ . Friction acts along the surface, against the sliding.

The worked solution

Have you tried it?

Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.

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← A 7.5 kg block rests on a floor with µs = 0.55 and µk = 0.42.A box of mass 18 kg is pulled at a steady speed across a floor by a rope at 28° above the… →

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