Question

A block of mass 3 kg is at rest on a rough inclined plane as shown in the figure. The magnitude of net force exerted by the surface on the block will be 

(A) 26N 

(B) 19.5N 

(C) 10N 

(D) 30N

Answer 1

Correct option is (d) 30 N

Now Balancing the forces parallel and perpendicular to the incline surface;

f = mg sin θ

N = mg cos θ

And Net force by surface = \(\sqrt{f^2 + N^2}\)

= \(\sqrt{(mg \sin \theta)^2 + (mg\cos\theta)^2}\)

= mg

= 30 N.

Answer 2

Correct answer is (d) 30 N