Answer:

Explanation:
Velocity of wave in stretched string is given by the formula

here we know that
T = 4 N
also we know that linear mass density is given as

so we have

now the tension in the string is double
so the velocity is given as


Quantity of Charge , Q = ne
Where n = number of electrons
e = charge on one electron = -1.6 * 10 ^-19 C.
n = 50 * 10^31 electrons
Q = (50 * 10^31)*( -1.6 * 10 ^-19 ) = -8 * 10^13 C.
Note that the minus sign indicates that the charge is a negative charge.
Answer:

Explanation:
As we know that thermal expansion coefficient of aluminium is given as

now we also know that after thermal expansion the final length is given as

here we know that



now we will have


When someone is struct by lightning, the electricity passes through the body, into the earth. Here, our body acts as a lightning conductor to complete the earthing process.
2. The zeros in front do not matter