Answer:
The mass of the Al-duckie should be 30 kg.
Explanation:
We will use the first law of thermodynamics:
ΔU = m·Cv·ΔT
Since the specific heat of water is 4.185 J(gºC), the change in the water's internal energy would be:
ΔU = 100 kg · 4.185 J(gºC) · (42ºC - 38ºC) = 1674 KJ
Given that no heat is lost, all the internal energy that the water loses while cooling down will transfer to the duckie. So, if the duckie has ΔU = 1674 KJ and its final temperature is the desired 38 ºC, we can calculate its mass using the first law again:
![m=\frac{\Delta{U}}{Cv{\Delta{T}}}=\frac{1674}{0.9*[38-(-24)]}=30Kg](https://tex.z-dn.net/?f=m%3D%5Cfrac%7B%5CDelta%7BU%7D%7D%7BCv%7B%5CDelta%7BT%7D%7D%7D%3D%5Cfrac%7B1674%7D%7B0.9%2A%5B38-%28-24%29%5D%7D%3D30Kg)
Answer:
Using Faraday's law;
ε= -N ∆ψ(B)/ ∆t;
∆t= -N ∆ψ(B)/ ε
Explanation:
Using Faraday's law; Faraday's law state that the induced emf is directly proportional to the rate of change of time of magnetic flux
ε= -N ∆ψ(B)/ ∆t;
Where ε= induced EMF, ∆ψ(B)/ ∆t is the rate of change of magnetic flux, ψ(B) = BA cos θ
θ= the angle between the magnetic field B and the normal surface area.
We can also calculate the direction of induced magnetic flux. At first, the field is perpendicular to the plane of the loop,the loop can rotate about either an horizontal or vertical axis passing through the mid point
D, because the hairdryer uses a fan
E, because it produces heat
Answer : Capacitors
Explanation : Capacitors are normally placed on transmission or distribution lines when to reduce inductive reactance.
This is because it enhances electromechanical and voltage stability , limit voltage dips at network nodes and reduces the power loss.
So, we can say that inductive reactance normally replace by the capacitors.
Answer:
less than 20580 N
Explanation:
According to the newton's second law of motion
Force = mass * acceleration
(assuming gravitational acceleration =9.8 m/s2 )
acceleration = 30*9.8 = 294 m/s2
acting Force = 70 * 294
= 20580 N
Since the acceleration was less than 30g , acting force should also be less than 20580 N
