An 8000 kg car moving at a constant speed of 14m/s strikes a barrier. The two stick together and move for a while at a speed of 5m/s. What is the mass of the barrier?
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Answer:
Initial velocity of car u = 20 m/s.
Final velocity =v= 0
Distance traveled after applying brakes = s = 50 m
The third equation of motion is: v^2 = u^2 +2 × a ×s
0^2 = 20^2 +2×a×50.
0 = 400 + 100×a
-400 = 100 a
a = - 400/100 - 4m/s^2
Force = m× a =1000 kg × (-4)m/s^2 = -4000 kgm/s^2
Force = - 4000 Newton's
Negative sign shows that force direction is opposite to velocity direction.