Answer:

Explanation:
Let the child is moving with speed same as the speed of water flow
So here the position of child with respect to flow must be zero
And if the boat start at an angle with the vertical
so its relative speed with flow of water is given as


now the time to reach the child is given as

so now we have

So the time to catch the child is given as


So distance moved by it in 0.104 h
distance moved by the boat in upstream direction given as


In y direction the displacement of boat is

net displacement of the ball is given as



ball drops 45m under g=10m/s/s
45=1/2x10xt^2 ... application of kinematic equaion from rest
90/10=t^2
t=3
24.0 m in 3 secs => 8m/s no air resistance
Answer:
A. a motor
Explanation:
A motor is an electrical device or machine that converts electrical energy into mechanical energy. That is, a motor takes electrical energy to produce motion. There are different types of motors such as DC motor, induction motor and so on.
When electrical current flows through a coil, a magnetic flux is been produced, therefore when a rotating power source is supplied to coil of a motor, a magnetic field is produced which causes torque.
Wave speed = (frequency) x (wavelength)
= (266 /sec) x (1.3 meters)
= 345.8 meters/sec