Calculating the corresponding percentage

[adam640]

Homework Statement

A car is traveling at initial speed 5.5ms^-1. The car is on a decline of 8^o. The brakes are used and the car stops after traveling 10m along the road (with no skidding).

At the moment when kinetic energy is 51% lower than the initial value,
find the corresponding percentage fall in speed.

Homework Equations

E_k = 1/2mv²

The Attempt at a Solution

E is 51% lower, so $$\frac{2(0.49)Ek}{m}$$=v²
Clueless?!

 

[verty]

Start with

$$\frac{Ek_2}{Ek_1}=\frac{49}{100}$$

From that relationship, get a relationship between the two velocities.