Answer:
30.93 m/s
Explanation:
Given that, the speed of stolen car is,

As policeman start chasing the stolen car after 60 seconds.
Now suppose the speed of policeman car is, 
The policeman catches the stolen car at a distance of,

Now the distance covered by the policeman in time t is 
And the distane cover by the thief in stolen car in time(t+60s) is
.
And these distances are equal and they are equal to 60000 m.
Therefore,

Therfore,

Now use this value to solve for minimum speed of policeman's car.

Therefore minimum speed of policeman's car is 30.93 m/s.
The amplitude of a wave corresponds to its maximum oscillation of the wave itself.
In our problem, the equation of the wave is
![y(x,t)= (0.750cm)cos(\pi [(0.400cm-1)x+(250s-1)t])](https://tex.z-dn.net/?f=y%28x%2Ct%29%3D%20%280.750cm%29cos%28%5Cpi%20%5B%280.400cm-1%29x%2B%28250s-1%29t%5D%29)
We can see that the maximum value of y(x,t) is reached when the cosine is equal to 1. When this condition occurs,

and therefore this value corresponds to the amplitude of the wave.
Answer:
Part a)

Part b)

Explanation:
As we know that electric force on electric charge is given as

here we have

E = 153 N/C
now force is given as

Gravitational force on electric charge near surface of earth is given as


now the ratio of two forces is given as


Part b)
Now the ball is balanced by the electric force and the force of gravity on it
so here we have



here we have
