Question

A ball has a speed of 15 m/s. Only one external force acts on the ball. After this force acts, the speed of the ball is 7 m/s. Has the force done positive, zero, or negative work on the ball?

Answer 1

Negative work

Step-by-step explanation:

The work-energy theorem states that the work of the resultant forces acting on a particle modifies its kinetic energy:

`W=\Delta K\\W=(mv_f^2)/(2)-(mv_0^2)/(2)\\W=(m)/(2)(v_f^2-v_0^2)\\W=(m)/(2)((7(m)/(s))^2-(15(m)/(s))^2)\\W=(m)/(2)(-178(m^2)/(s^2))`

Since the mass of the ball has to be positive, the work is negative.