A frictionless vertical post is inserted into a bowling ball with a hole drilled through its center. The ball has a mass of 10.5 kg. A rope is attached to a ring that has been affixed to the ball....

A frictionless vertical post is inserted into a bowling ball with a hole drilled

through its center. The ball has a mass of 10.5 kg. A rope is attached to a

ring that has been affixed to the ball. Kurt pulls on the rope at an angle of

(theta)= 24.5° with respect to the vertical with a constant force of

magnitude . F=134N

(a) How much work does Kurt do on the bowling ball by raising it through a vertical distance of 1.08 m at a
constant velocity?

(b) How much work does the Earth do on the ball while it is being raised through a distance of 1.08 m?

(c) Kurt is lazy and would like to be able to raise the ball through the same vertical distance with a minimum
effort. What two changes in his actions would you recommend to her?

(d) What is the net work done on the ball by the two forces acting on it?

(e) If Kurt raises the mass in a time of 0.56 s what is his horse power?

Expert Answers
justaguide eNotes educator| Certified Educator

A frictionless vertical post is inserted into a bowling ball with a hole drilled through its center. The ball has a mass of 10.5 kg. A rope is attached to a ring that has been affixed to the ball. Kurt pulls on the rope at an angle of 24.5 degrees. with respect to the vertical with a constant force of magnitude F = 134 N

The work done by the Earth when the ball is raised by a vertical distance of 1.08 m is equal to 10.5*9.8*-1.08 = -111.132 J

The component of the force in the vertically upwards direction is equal to 134*cos 24.5 = 121.9 N. The work done is equal to the dot product of force applied and the resulting displacement. If Kurt would like to use a minimum magnitude of force to lift the ball, the force should be applied in a vertically upwards direction instead of at an angle to the vertical.