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
D. 0.25 meters/second2
Explanation
The average acceleration is the ratio of change in velocity to the change in time of travel.Taking in this case that the change of velocity is a unit, then Average acceleration is given by;
Aacc=Vf-Vi/Tf-Ti
where Vf=final velocity,Vi=initial velocity' Tf=final time, Ti=initial time
Vf-Vi=1m/s
Tf-Ti=4-0=4seconds
Avacc=1/4=0.25m/s2
Answer:twice of initial value
Explanation:
Given
spring compresses
distance for some initial speed
Suppose v is the initial speed and k be the spring constant
Applying conservation of energy
kinetic energy converted into spring Elastic potential energy

When speed doubles

divide 1 and 2


Therefore spring compresses twice the initial value
Answer:
Induced current, I = 18.88 A
Explanation:
It is given that,
Number of turns, N = 78
Radius of the circular coil, r = 34 cm = 0.34 m
Magnetic field changes from 2.4 T to 0.4 T in 2 s.
Resistance of the coil, R = 1.5 ohms
We need to find the magnitude of the induced current in the coil. The induced emf is given by :

Where
is the rate of change of magnetic flux,
And 



Using Ohm's law, 
Induced current, 

I = 18.88 A
So, the magnitude of the induced current in the coil is 18.88 A. Hence, this is the required solution.
Answer:
4306.8625 J or 344549/80J (fraction form)
Explanation:
kinetic energy=
mv²
=
×72.5×10.9²
= 4306.8625 J or 344549/80 J