- #1
fizz123
- 6
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One car has twice the mass of a second car, but only half as much kinetic energy. When both cars increase their speed by 8.5 m/s, they then have the same kinetic energy. What were the original speeds of the two cars?
first i set it up like this:
.5 * m * v1^2 = .5 * (.5 * 2m * v2^2)
then i get:
v1 = v2
then
.5 * m * (v1 + 8.5)^2 = .5 * 2m * (v2 + 8.5)^2
.5 * (v1 + 8.5)^2 = (v2 + 8.5)^2
but its not right...
first i set it up like this:
.5 * m * v1^2 = .5 * (.5 * 2m * v2^2)
then i get:
v1 = v2
then
.5 * m * (v1 + 8.5)^2 = .5 * 2m * (v2 + 8.5)^2
.5 * (v1 + 8.5)^2 = (v2 + 8.5)^2
but its not right...