Answer to Question #256034 in Mechanics | Relativity for alyazya

Question

A horizontal force of 33.8 N is applied to a 5.8 kg box that slides on a horizontal surface. The box starts from rest moves a horizontal distance of 8.7 meters and obtains a velocity of 5 m/s. The surface has friction. The frictional force in newton is

Answer 1

Explanations & Calculations

• Considering the energy conservation for this motion, you can find the friction force that is applied throughout.
• The applied force (33.8 N) provides energy to increase the box's kinetic energy and to work against friction.

$\qquad\qquad \begin{aligned} \small Fs &=\small fs+\Delta K_e\\ &=\small fs+\frac{1}{2}mv^2\\ \small f&=\small \frac{Fs-0.5mv^2}{s}\\ &=\small \frac{33.8\,N\times8.7\,m-(0.5\times5.8\,kg\times(5\,ms^{-1})^2}{8.7\,m}\\ &=\small \bold{25.47\,N} \end{aligned}$