Bob and Biff throw identical rocks off a tall building at the same time.Bob throws his rock straight downward.Biff throws his rock downward and outward such that the angle between the initial velocity of the rock and the horizon is 30 degrees.Biff throws the rock with a speed twice that of Bob's rock.Which rock hits the ground first (assume the ground near the building is flat)?
A)They hit at the same time.
B)Bob's rock
C)Biff's rock
D)Impossible to determine

Question

Quizplus · Accepted Answer

The time it takes for an object to fall to the ground only depends on its vertical component of velocity, not on its horizontal component. Both rocks have the same vertical component of velocity, as they are dropped from the same height (assuming they are released at the same time). Therefore, both rocks hit the ground at the same time. The fact that Biff's rock has a higher initial velocity and a horizontal component does not affect the time it takes to fall to the ground.

Bob and Biff Throw Identical Rocks Off a Tall Building