A) 
The total energy of the system is equal to the maximum elastic potential energy, that is achieved when the displacement is equal to the amplitude (x=A):
(1)
where k is the spring constant.
The total energy, which is conserved, at any other point of the motion is the sum of elastic potential energy and kinetic energy:
(2)
where x is the displacement, m the mass, and v the speed.
We want to know the displacement x at which the elastic potential energy is 1/3 of the kinetic energy:

Using (2) we can rewrite this as

And using (1), we find

Substituting
into the last equation, we find the value of x:

B) 
In this case, the kinetic energy is 1/10 of the total energy:

Since we have

we can write

And so we find:

Answer
given,
mass of the goalie(m₁) = 70 kg
mass of the puck (m₂)= 0.11 kg
velocity of the puck = 31.5 m/s
elastic collision







Answer: The first electromagnet has a more powerful current than
the second
Explanation:
Since the two electromagnets contain the same types of magnets and wires. If the magnet In the first moves much faster than the second. Therefore:
The first electromagnet has a more powerful current than the second
Because the induced EMF is proportional to the induced current.
Where the induced EMF depends on the speed of the magnet according to the formula below
EMF = BVL
So, increase in speed of the magnet will cause more powerful induced current and emf
Your answer would be A. Halogens