Question

A 6.75 kg laundry bag is dropped from rest at an initial height of 5.97 m. The acceleration of gravity is -9.81 m/s^2. Use the value 5.98 x 10^24 kg as the mass of Earth. What is the speed of Earth toward the bag just before the bag hits the ground?

Answer 1

for the bag, v^2 = 2as = 2*9.81*5.97
v = 10.82 m/s
now, to conserve momentum, for the earth we need
6.75*10.82 = 5.98*10^24 * v
v = 1.22 * 10^-23 m/s