Answer:
The slower the train is moving, the less are the changes of the magnetic flux, thus the eddy currents become weaker.
Explanation:
A magnetic brakes is not a very efficient way of braking when a train is moving slowly because at low speeds, the changes in the magnetic flux are very less and so it causes the eddy current to become weaker.
Let us find the drag force which is proportional to the velocity of two conducting plates.
The EMF that is induced in the eddy currents are : 
The force which is due to the induced magnetic field is, 
Therefore, 

Here, force is directly proportional to the velocity of the two conducting plates.
Therefore, we can say that when the speed of the train is low, the magnetic flux changes are less and thus the eddy currents are weaker.
Answer:
A) Magma emplacement
Explanation:
Sedimentary structures forms during deposition of sediments. It can also form after sediments have been deposited. Sedimentary structures can only be found in sedimentary rocks. Some examples include mud cracks, ripple marks, cross stratification, potholes, etc
Magma emplacement is an igneous process which describes the different mechanisms by which magma can be emplaced. It is only typical of igneous rocks.
Answer:
Change in Potential energy, pe = Final potential energy - Initial potential energy
Explanation:
∆p.e = Final p.e - Initial p.e
From the equation ∆p.e = (mgh) final - (mgh) initial
a) 10 m/s
b) 25 m
Explanation:
a)
The body is moving with a constant acceleration, therefore we can solve the problem by using the following suvat equation:

where
u is the initial velocity
v is the final velocity
a is the acceleration
t is the time
For the body in this problem:
u = 0 (the body starts from rest)
is the acceleration
t = 5 s is the time
So, the final velocity is

b)
In this second part, we want to calculate the distance travelled by the body.
We can do it by using another suvat equation:

where
u is the initial velocity
v is the final velocity
a is the acceleration
s is the distance travelled
Here we have
u = 0 (the body starts from rest)
is the acceleration
v = 10 m/s is the final velocity
Solving for s,

Explanation:
electricity is the flow of electrical power or charge