Answer:
<em>The average speed of the train is 45 km/h</em>
Explanation:
<u>Speed</u>
It's defined as the distance (d) per unit of time (t) traveled by an object. The formula is:

Let's call x the total distance covered by the train. It covered d1=1/3x with a speed of v1=25 km/h. The time taken is calculated solving for t:



Now the rest of the distance:
d2 = x - 1/3x = 2/3x
Was covered at v2=75 km/h. Thus the time taken is:



The total time is:



Simplifying:

The average speed is the total distance divided by the total time:

Simplifying:

The average speed of the train is 45 km/h
Answer:
A) coil A
Explanation:
According to Faraday, Induced emf is given as;
E.M.F = ΔФ/t
ΔФ = BACosθ
where;
ΔФ is change in magnetic flux
θ is the angle between the magnetic field, B, and the normal to the loop of area A
A is the area of the loop
B is the magnetic field
From the equation above, induced emf depends on the strength of the magnetic field.
Both coils have the same area and are oriented at right angles to the field.
Coil A has a magnetic field strength of 10-T which is greater than 1 T of coil B, thus, coil A will have a greater emf induced in it.
Answer:
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To solve this exercise we will use the concept related to heat loss which is mathematically given as

Where,
m = mass
= Specific Heat
Change in temperature
Replacing with our values we have that

Specific heat of mercury

Replacing

Therefore the heat lost by mercury is 0.09J
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