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
be the angle .
Therefore,



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



Answer is 76,352 just look it up
By law of refraction we know that image position and object positions are related to each other by following relation

here we know that



now by above formula


so apparent depth of the bottom is seen by the observer as h = 3.39 cm
Answer:
The string will break with a speed of 20 m/s.
Explanation:
It is given that,
Tension at which the string just breaks, T = 400 N
Mass of the stone, m = 10 kg
Radius of the circle, r = 10 m
We need to find the speed at which the string will break. The boy continuously increases the speed of the stone. The tension acting on the stone is equal to the centripetal force. It is a force that acts towards the center of circle. It is given by :



v = 20 m/s
So, the string will break with a speed of 20 m/s. Hence, this is the required solution.