That is the Sigma Symbol. It’s the addition of a sequence of numbers; the result is the sum of the total. if numbers are added sequentially from left to right, any intermediate result is a partial sum, prefix sum, or running total of the summation
Answer: Katherine Johnson's knowledge of (mathematics) was instrumental in the return of the Apollo astronauts from the Moon to Earth.
Given
Car 1
m1 = 1300 kg
v1 = 20 m/s
m2 = 900 kg
v2 = -15 m/s
(Negative sign shows that direction of car 2 is opposite to car 1)
Procedure
As per the conservation of linear momentum, "The total momentum of the system before the collision must be equal to the total momentum after the collision". And this applies to the perfectly inelastic collision as well. Then the expression is,

Thus, we can conclude that the speed and direction of the cars after the impact is 5.68 m/s towards the first car.
Answer:
Radiation heat energy transfer
Explanation:
The type of heat transfer from the Sun is radiation heat transfer, which is the transfer of heat through electromagnetic radiation
The distance of the Sun to the Earth is several million kilometers away, with the space between being composes of vacuum and the nuclear reaction in the Sun's core generates vast amount of electromagnetic radiation that is transferred all across the universe and reaches the Earth as visible light and radiant energy at the speed of light
The radiant energy transferred from the Sun heats up the Earth, including the car's interior.