A 1,250-kg car traveling initially with a speed of 25.0 m/s in an easterly direc
ID: 1902564 • Letter: A
Question
A 1,250-kg car traveling initially with a speed of 25.0 m/s in an easterly direction crashes into the rear end of a 9,700-kg truck moving in the same direction at 20.0 m/s. The velocity of the car right after the collision is 18.0 m/s to the east.(a) What is the velocity of the truck right after the collision?
m/s (east)
(b) How much mechanical energy is lost in the collision? (Use input values with an adequate number of significant figures to calculate this answer.)
kJ
(c) Account for this loss in energy.
Explanation / Answer
A 1,115-kg car traveling initially with a speed of 25.0 m/s in an easterly direction crashes into the rear end of a 9,400-kg truck moving in the same direction at 20.0 m/s (see figure below). The velocity of the car right after the collision is 18.0 m/s to the east. I know that the mechanical energy lost in the collision is 10086J. In kJ my answer would be 10.086kJ. But, I need to use input values with adequate number of sig figs in my answer. In that case, what would be my answer? Speed of the truck after the collision is given by m(c) . v(c) + m(t) . v(t) = m(c) . V (c) + m(t) . V(t) 1115 . 25 + 9400. 20 = 1115 . 18 + 9400 . V(t) V(t) = 20.83 m/s KE lost = KE before – KE after KE lost = (1/2 . 1115 . 25^2 + 1/2 . 9400 . 20^2) – ( 1/2 . 1115 . 18^2 + 1/2 . 9400 . 20.83^2 ) Just do this and round to 3 sig figs.... that should be it.
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