Answer:
instantaneous velocity is a velocity covered at an instant while average velocity is the change in distance/ the change in time taken
225 = 1/2 (50) (v2)
225 = 25 (v2)
225/25 = v2
9 = v2
√9 = v
v = 3 m/s
At the point of maximum displacement (a), the elastic potential energy of the spring is maximum:

while the kinetic energy is zero, because at the maximum displacement the mass is stationary, so its velocity is zero:

And the total energy of the system is

Viceversa, when the mass reaches the equilibrium position, the elastic potential energy is zero because the displacement x is zero:

while the mass is moving at speed v, and therefore the kinetic energy is

And the total energy is

For the law of conservation of energy, the total energy must be conserved, therefore

. So we can write

that we can solve to find an expression for v:
Newton' 1st Law of Motion
A soccer ball will not move until a player kicks it
A bowling ball hits the pins sending the pins flying for a STRIKE!
Newton's 2nd Law of Motion
it takes less force to move a ping pong ball then a bowling ball.
f - ma
Newton's 3rd Law of Motion
a fireman turns on his house and is knocked backward
If air is let out of a balloon quickly, air pushes down & balloon goes up
E = hf
E = 6.63×10^-34 × 3.55×10 eV
1 eV = 1.60×10^-19 J
E = 6.63×10^-34 × 3.55×10 × 1.60×10^-19
E = 3.77×10^-51 J
Hope it helped!