Q19DQ - University Physics with Modern Physics

Question

From the top of a tall building, you throw one ball straight up with speed ${\mathit{v}}_{\mathbf{0}}$ and one ball straight down with speed ${\mathit{v}}_{\mathbf{0}}$.

(a) Which ball has the greater speed when it reaches the ground?

(b) Which ball gets to the ground first? (c) Which ball has a greater displacement when it reaches the ground? (d) Which ball has traveled the greater distance when it hits the ground?

Step-by-Step Solution

Answer

(a). Both the balls have the same speed when they reach the ground.

(b). The ball thrown straight down will reach the ground first.

(c). The displacement of both balls will be equal.

(d). The ball which was thrown straight up travels a greater distance.

Part (a)

Both balls have the same speed when they reach the ground. The ball that is thrown straight up will come to a stop at its highest point, then it will speed $v_0$ up as it drops. This ball will have the speed when it reaches the top of the building again.

Part (b)

The ball thrown straight down will reach the ground first because the ball thrown straight up takes a detour before heading down to the ground.

Part (c)

The displacement of both balls will be equal to the distance from the top of the building to the bottom of the building.

Part (d)

The ball which was thrown straight up travels a greater distance because it goes up to its maximum height and then falls back down. The ball which is thrown straight down travels a distance equal to the height of the building.