Answer:
The average force exerted on the window due to two snowballs is 6 N
Explanation:
Given:
Mass of snowballs
Kg
Velocity of snowball 
For finding the average force,
Force is equal to the change in momentum,

Here, final velocity is zero so we write,

Where
sec

N
Above value of force is due to one ball, but here given in question there are two ball,

N
Therefore, the average force exerted on the window due to two snowballs is 6 N
Answer: There are number of electrons.
Explanation:
We are given 50 Coulombs of charge and we need to find the number of electrons that can hold this much amount of charge. So, to calculate that we will use the equation:
where,
n = number of electrons
Charge of one electron =
Q = Total charge = 50 C.
Putting values in above equation, we get:
Hence, there are number of electrons.
Answer:
b) 5 J
Explanation:
Work is the energy transferred by an object when acted by a force along a displacement. Work is the product of force and displacement. The SI unit of work is the joules (J)
To calculate the work done by the force, we have to first get the displacement (D) of the object. Hence:
Displacement (D) = Q(3, 8) - P(1, 3) = (3 - 1, 8 - 3) = (2, 5) = 2i + 5j
The work done is the dot product of the force and the displacement. Force = 5i - j. Hence:
Work done = (5i - j)(2i + 5j) = 10 - 5 = 5 J
Efficiency is calculated through dividing the actual mechanical advantage by the hypothetical mechanical advantage:
- the actual mechanical advantage is 9J because that's how much work the light bulb doing
- the hypo. mechanical advantage is 100J. Ideally, in a perfect world, the light bulb can convert 100J input into 100J output, but do to resistance and other factors it is not possible.

change the decimal to a percentage:

the light bulb had 9% efficiency
The water will be cool and steam will be created by the hot and cold water reacting together