question_answer

A body of weight \[50\,\,N\] placed on a horizontal surface is just moved by a force of\[28.2\,\,N\]. The frictional force and normal reaction are

A) \[2N,\,\,3N\]                    

B) \[5N,\,\,6N\]

C)  \[10N,\,\,15N\]                               

D)  \[20N,\,\,30N\]

Correct Answer: D

Solution :

Frictional-force,\[f=28.2\,\,\cos {{45}^{o}}\]                 \[=28.2\frac{1}{\sqrt{2}}=20\,\,N\] Normal reaction,\[R=50-28.2\sin {{45}^{o}}\]                 \[=50-20=30\,\,N\]