physics
posted by tanya .
a sled slides down a frictionless hill. if the sled starts from rest at the top, its speed is 7.5 m/s.
a.) on a second run , the sled starts with a speed of 1.5 m/s at the top.. will it end with less than 9 m/s, 9 m/s, or more than 9 m/s
b.) find the speed of the sled at the bottom of the hill after the second run

physics 
drwls
Before trying to answer (a), let's do (b).
Due to the starting kinetic energy, the KE at the bottom will be increased from
(1/2)M(7.5)^2 to (1/2)M[(1.5)^2 + (7.5)^2] = (1/2)M(58.5) = (1/2)M(7.64)^2
The velocity at the bottom in the second case will be 7.64 m/s.
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