Forces

When the block slides down with uniform speed, the forces acting along the plane and perpendicular to the plane must balance.
The contact force is the resultant of the normal force and the frictional force.
The frictional force is given by: The component of gravitational force along the plane is: Since the block moves with uniform speed, the net force along the plane must be zero, so the contact force is the resultant of these two forces:
Thus, the correct answer is (d).

The gravitational acceleration on an asteroid is the same in all directions regardless of the direction of motion. This is because the gravitational field is uniform and acts equally in every direction. When an object is thrown upward, it experiences the same gravitational acceleration as when it is dropped freely, which is directed downward. The key difference is in the motion of the object due to the initial velocity.

When the wrench is thrown upward, the effective acceleration decreases because of the initial upward velocity. The wrench starts with an upward velocity that opposes the gravitational pull, causing the object to slow down. As the wrench rises, the downward gravitational acceleration causes it to decelerate. Once it reaches the peak, the object begins to accelerate downward. However, due to the initial upward motion, the observed acceleration is smaller than the full gravitational acceleration (2.4 m/s²).

Hence, the correct answer is (a).