Question

A car has a kinetic energy of 25 J. It then makes a U-turn and moves in the opposite direction with twice the original speed. What is the new kinetic energy of the car

Answer 1

The new kinetic energy of the car is of 100 Joules.

Step-by-step explanation:

According to the question:

After a U-turn the speed of the car is twice of the original.

Lets assume that the original speed of the car be "v"

And the mass of the car be "m"

Kinetic energy of the car,
`K_1` = 25 J

In terms of formula we can also say that:

⇒
`K_1=(mv^2)/(2)`

⇒
`K_1=25` J ...equation(i)

Now as the speed is twice of the original so it is "2v".

And its kinetic energy =
`K_2` .

⇒
`K_2=(m(2v)^2)/(2)`

⇒
`K_2=(4mv^2)/(2)` ...equation (ii)

Dividing (ii) with (i)

⇒
`(K_2)/(K1) = (4mv^2)/(2)* (2)/(mv^2)`

⇒
`(K_2)/(K_1) =(4)/(1)`

⇒
`K_2=4K_1`

⇒Plugging the value of
`K_1=25` J

⇒
`K_2=4(25)`

⇒
`K_2=100` J

The new kinetic energy of the car = 100 Joules.