Answer:
(i) The wavelength is 0.985 m
(ii) The frequency of the wave is 36.84 Hz
Explanation:
Given;
mass of the string, m = 0.0133 kg
tensional force on the string, T = 8.89 N
length of the string, L = 1.97 m
Velocity of the wave is:

(i) The wavelength:
Fourth harmonic of a string with two nodes, the wavelength is given as,
L = 2λ
λ = L/2
λ = 1.97 / 2
λ = 0.985 m
(ii) Frequency of the wave is:
v = fλ
f = v / λ
f = 36.29 / 0.985
f = 36.84 Hz
Answer:
mu=12Tm^2
Explanation:
the magnetic moment mu of a single loop is given by:

where I is the current, B is the magnetic field and A is the area of the loop. By replacing we obtain:

hope this helps!!
Answer:
Power_input = 85.71 [W]
Explanation:
To be able to solve this problem we must first find the work done. Work is defined as the product of force by distance.

where:
W = work [J] (units of Joules)
F = force [N] (units of Newton)
d = distance [m]
We need to bear in mind that the force can be calculated by multiplying the mass by the gravity acceleration.
Now replacing:
![W = (80*10)*3\\W = 2400 [J]](https://tex.z-dn.net/?f=W%20%3D%20%2880%2A10%29%2A3%5C%5CW%20%3D%202400%20%5BJ%5D)
Power is defined as the work done over a certain time. In this way by means of the following formula, we can calculate the required power.

where:
P = power [W] (units of watts)
W = work [J]
t = time = 40 [s]
![P = 2400/40\\P = 60 [W]](https://tex.z-dn.net/?f=P%20%3D%202400%2F40%5C%5CP%20%3D%2060%20%5BW%5D)
The calculated power is the required power. Now as we have the efficiency of the machine, we can calculate the power that is introduced, to be able to do that work.
![Effic=0.7\\Effic=P_{required}/P_{introduced}\\P_{introduced}=60/0.7\\P_{introduced}=85.71[W]](https://tex.z-dn.net/?f=Effic%3D0.7%5C%5CEffic%3DP_%7Brequired%7D%2FP_%7Bintroduced%7D%5C%5CP_%7Bintroduced%7D%3D60%2F0.7%5C%5CP_%7Bintroduced%7D%3D85.71%5BW%5D)
The 4 significant figures of 31,546,000 are all 8 of the digits.