Question

Three students have been studying relative motion and decide to do an experiment to demonstrate their knowledge. The experiment plan calls for Jane to drive her pickup in a straight line across the parking lot at a constant speed of 12.6 m/s. Fred is in the back of the truck and throws a baseball backward and upward at an angle ? out the back of the truck. Sue observes the flight of the ball while standing nearby in the parking lot.
(a) If Fred can throw the ball 30.0 m/s, at what angle relative to the horizontal should he throw the ball in order for Sue to see the ball travel vertically upward? (Enter your answer to at least one decimal place.)
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(b) If Fred throws the ball at this angle, how high does Sue observe it to travel above the level at which it was thrown?

Answer 1

Answer with Explanation:

We are given that

Constant speed of Jane=12.6 m/s

a.When Fred can throw the ball 30  m/s

We have to find the angle relative to the horizontal when he throw the ball in order for Sue to see the ball travel vertically upward.

Let $\theta$ be the angle .

Therefore,

$30 cos\theta=12.6$

$cos\theta=\frac{12.6}{30}=0.42$

$\theta=cos^{-1}(0.42)=65.165^{\circ}$

b.We have to find the height to which ball reach.

$v^2-v^2_0=2aS$

$S=\frac{v^2-v^2_0}{2a}=\frac{0-(30 sin65.165)^2}{2(-9.81)}$

$S=37.78 m$