Acar with a mass of 1.1 × 103 kilograms hits a stationary truck with a mass of 2.3 × 103 kilograms from the rear end. the initial velocity of the car is +22.0 meters/second. after the collision the velocity of the car is -11.0 meters/second. what is the velocity of the truck after this elastic collision?
a. +13 meters/second
b. +20 meters/second
c. +15.7 meters/second
d. +7.5 meters/second
e. +9.8 meters/second

The velocity of the truck after this elastic collision is 15.7 m/s            

Explanation:

It is given that,

Mass of the car,

Mass of the truck,

Initial velocity of the car,

Initial velocity of the truck, u₂ = 0

After the collision the velocity of the car is, v₁ = -11 m/s

Let v₂ is the velocity of the truck after this elastic collision. Using the conservation of momentum as :

So, the velocity of the truck after this elastic collision is 15.7 m/s. Hence, the correct option is (c).

the old price per ounce is c/4.

the new price per ounce is c/3.6.

the ratio of the old price to the new one is

(c/4)/(c/3.6) = (c/c)×(3.6/4) = 0.9 . . = 9/10 . . "nine tenths" in either form