When dropped from the same height, a hammer and feather fall at the same rate of acceleration in the absence of air friction and reach the ground at the same time. Why?

Amira pulls a 3 pound wagon 4 feet. how much work has she done?

Two resistors r1 and r2 may be connected either in series or parallel across an ideal battery with emf ε. we desire the rate of energy dissipation of the parallel combination to be 8.75 times that of the series combination. if r1 = 105 ω, what are the (a) smaller and (b) larger of the two values of r2 that result in that dissipation rate?

What is the coefficient of kinetic friction μk between the block and the tabletop?