If a pulley with six supporting ropes is used to lift a 1200 lb piano, what input force is needed?

a 1800 lbs
b 500 lbs
c 300 lbs
d 200 lbs

Which explanation describes the forces involved for a person to walk down the sidewalk? a. the person's feet push backward on the sidewalk; the sidewalk pushes backward on the person. b. the person's feet push forward on the sidewalk; the sidewalk does not push on the person. c. the person's feet push backward on the sidewalk; the sidewalk pushes forward on the person. d. the person's feet push forward on the sidewalk; the sidewalk pushes forward on the person.

Ajoint produces movement when its angle decreases. which type of movement is it?

What efficiency of a car's engine when heat input is 200,000 joules and waste heat is 150,000 joules? a. 75% b. 35% c. 25% d. 85%