Answer:
v₃ = 22.67 [m/s]
Explanation:
In order to solve this problem, we must use the principle of conservation of the quantity of linear momentum. Where momentum is conserved before and after the collision, i.e. remains the same.
The terms on the left of the equation represent the amount of linear momentum before the collision and the members on the right represent the momentum after the collision.

where:
m₁ = mass of the truck = 3000 [kg]
m₂ = mass of the car = 1000 [kg]
v₁ = velocity of the truck before the coliision = 25 [m/s]
v₂ = velocity of the car parked = 0 (without movement)
v₃ = velocity of the truck after the collision [m/s]
v₄ = velocity of the car after the collision = 7 [m/s]
Now replacing:
![(3000*25)+(1000*0)=(3000*v_{3})+(1000*7)\\75000-7000 = 3000*v_{3}\\v_{3}=22.67 [m/s]](https://tex.z-dn.net/?f=%283000%2A25%29%2B%281000%2A0%29%3D%283000%2Av_%7B3%7D%29%2B%281000%2A7%29%5C%5C75000-7000%20%3D%203000%2Av_%7B3%7D%5C%5Cv_%7B3%7D%3D22.67%20%5Bm%2Fs%5D)
A light-year is how astronomers measure distance in space.
-Light can travel 300,000 kilometres in one seconds!
Light year is the distance that light travel can travel in one year.
-Light can also travel 9,00,000,000,000 kilometers.
-One light is about 10 trillion km.
-Almost 300 years ago ,a Danish scientist named olaus roemer,was the fist man to estimate the distance light travels in a year -and using that he figure out the approximate speed of light!
Explanation:
the other 40% is used to power the 60% making it only capable of 60% efficiency