Question

A brick of mass $2$ $kg$ just begins to slide down on inclined plane at an angle of ${45}^o$ with the horizontal and coefficient of friction is 1. The force of friction will be

• A. 19.6 tan ${45}^o$
• B. 9.8 sin ${45}^o$
• C. 19.6 cos ${45}^o$
• D. 9.8 cos ${45}^o$

Answer 1

Answer: (C)

19.6 cos ${45}^o$

Resolving weight into its sine and cosine components, we get,
Frictional force =$\mu N$$=\mu mg\cos \theta \Rightarrow 19.6cos{45}^o$