A boy throws a steel ball straight up. Consider the motion of the ball only after it has left the boy's hand but before it touches the ground, and assume that forces exerted by the air are negligible. For these conditions, the force(s) acting on the ball is (are): a) a downward force of gravity along with a steadily decreasing upward force.
b) a steadily decreasing upward force from the moment it leaves the boy's hand until it reaches its highest point; on the way down there is a steadily increasing downward force of gravity as the object gets closer to the earth.
c) an almost constant downward force of gravity along with an upward force that steadily decreases until the ball reaches its highest point; on the way down there is only a constant downward force of gravity.
d) an almost constant downward force of gravity only.
e) none of the above. The ball falls back to the ground because of its natural tendency to rest on the surface of the earth.

c) an almost constant downward force of gravity along with an upward force that steadily decreases until the ball reaches its highest point; on the way down there is only a constant downward force of gravity.

Explanation:

When the boy throws the ball upward, there are two forces acting on the ball. First one is the force of gravity, which is constant and equal tot he weight of the ball, acting down. The second force is the force with which the boy throws the ball. This force acts upward and decreases as the ball moves up. This force becomes zero when the ball reaches highest point.

While, on its way down the ball has only one force acting on it. That force is the constant force of gravity acting downward. This gravity force is equal to the weight of the ball.

Hence, the correct option is:

c) an almost constant downward force of gravity along with an upward force that steadily decreases until the ball reaches its highest point; on the way down there is only a constant downward force of gravity.