First, let's calculate the total mechanical energy when the block is at rest and the spring is compressed 5 cm:

Now, let's use this total energy to calculate the velocity when the spring is compressed by 2.5 cm:

Therefore the speed is 1.026 m/s.
Answer:
0.099C
Explanation:
First, we need to get the common potential voltage using the formula

Where V is the common voltage, C and V represent capacitance and charge respectively. Subscripts 1 and 2 to represent the the first and second respectively. Substituting the above with the following given values then

Therefore

Charge, Q is given by CV hence for the first capacitor charge will be 
Here, 
Answer:
Gravity, Weak, Electromagnetic and Strong.