Question

A box is placed on a flat surface. Jane lifts one end of the surface, making an angle with the floor. As she increases the angle that the surface makes with the floor, the box eventually begins to slide down because..
A- only coefficient of static friction decreased

B- only normal force exerted by the board decreased

C- component of the gravitational force parallel to the plane increased, coefficient of static friction decreased and normal force exerted by the board decreased

D- component of the gravitational force parallel to the plane increased and normal force exerted by the board decreased

E- only component of the gravitational force parallel to the plane increased

Answer 1

Answer:

D- component of the gravitational force parallel to the plane increased and normal force exerted by the board decreased

Explanation:

component of the gravitational force parallel to the plane = mg sinθ  ;  where θ is inclination of the plane . As it increases , sinθ increases and hence component of the gravitational force parallel to the plane increases .

normal force exerted by the board = mg cosθ . As θ increases , cosθ decreases and hence normal force exerted by the board decreases and hence friction force decreases because

Friction force = coefficient of friction x normal force exerted by the board .

coefficient of friction remains constant.