At the gym, a man pulls a bar on a machine that works the muscles of the upper back. It takes him 0. 5 seconds to raise 30 kilograms of weights a vertical distance of 0. 5 meters.

Which of these exerts the same power output? (Estimate g as 10 m/s2. )

A) lifting 25 kilograms a distance of 2. 4 meters in 2. 0 seconds

B) lifting 45 kilograms a distance of 2. 4 meters in 3. 0 seconds

C) leg pressing 45 kilograms a distance of 0. 5 meters in 0. 5 seconds.

D) bench pressing 30 ligrograms a distance of 0. 5 meter in 1. 5 seconds.

Pleas help me

Where is the potential energy throughout the loading, cocking, and releasing of the trebuchet?

Electric field of the earth. the earth has a net electric charge that causes a field at points near its surface equal to 150 n> c and directed in toward the center of the earth. (a) what magnitude and sign of charge would a 60-kg human have to acquire to overcome his or her weight by the force exerted by the earth’s electric field? (b) what would be the force of repulsion between two people each with the charge calculated in part (a) and separated by a distance of 100 m? is use of the earth’s electric field a feasible means of flight? why or why not?

Consider a uniformly charged ring in the xy plane, centered at the origin. the ring has radius a and positive charge qdistributed evenly along its circumference. a)what is the direction of the electric field at any point on the z axis? . b)what is the magnitude of the electric field along the positive z axis? use k in your answer, where k=14πϵ0. d)the ball will oscillate along the z axis between z=d and z=−d in simple harmonic motion. what will be the angular frequency ω of these oscillations? use the approximation d≪a to simplify your calculation; that is, assume that d2+a2≈a2. express your answer in terms of given charges, dimensions, and constants