The Doppler effect happens as the result of a source of waves having relative motion to observers somewhere else consider that if something is producing a wave of wavelength W and it is moving relative to the waves then as the waves spread out it seems to chase one side and run away from the other side there for wavelengths produced on the scale it is chasing will be less than W on the side it is running away from the apparent wavelength will be greater than W so using this knowledge if the source of the Waves moves faster than it will chase one of the more closely and run away from the other more quickly there for making the short wavelength even shorter and the long wavelength even longer can turn you in and tell you have gone all over the speed of wave creating boom when dealing with sound this is what causes a sonic boom this lengthening of the long wavelengths and the shortening of the short wavelengths is referred to as being a greater Doppler shift
(a) 392 N/m
Hook's law states that:
(1)
where
F is the force exerted on the spring
k is the spring constant
is the stretching/compression of the spring
In this problem:
- The force exerted on the spring is equal to the weight of the block attached to the spring:

- The stretching of the spring is

Solving eq.(1) for k, we find the spring constant:

(b) 17.5 cm
If a block of m = 3.0 kg is attached to the spring, the new force applied is

And so, the stretch of the spring is

And since the initial lenght of the spring is

The final length will be

Answer:
the work done by the 30N force is 4156.92 J.
For this problem, they don´t ask you to determine the work of the total force applied in the block. They only want the work done for the force of 30N, with an angle of 30º respectively of the displacement and a traveled distance of 160m. So:
W=F·s·cos(α)=30N·160m·cos(30º)=4156.92J
Answer:
22.05 Kg
Explanation:
Apply the formula:
GPE = Gravity . Mass . ΔHigh
2778.3 = 10 . Mass . 12.6
2778.3 = 126 . Mass
Mass = 2778.3/126
Mass = 22.05