Answer:
118.3 J
Explanation:
Givens:
m = 1.4 kg
V = 13 m/s
Formula for kinetic energy:
KE = (1/2)*(m)*(v)^2
KE = .5*(1.4 kg)*(13 m/s)^2
KE 118.3 J
J = Joules
Power = (voltage) x (current)
Power = (240 volts) x (4 Amp)
Power = 960 watts
Note: I'm not sure what do you mean by "weight 0.05 kg/L". I assume it means the mass per unit of length, so it should be "0.05 kg/m".
Solution:
The fundamental frequency in a standing wave is given by

where L is the length of the string, T the tension and m its mass. If we plug the data of the problem into the equation, we find

The wavelength of the standing wave is instead twice the length of the string:

So the speed of the wave is

And the time the pulse takes to reach the shop is the distance covered divided by the speed: