In: Physics
An electric vehicle starts from rest and accelerates at a rate of 2.4 m/s2 in a straight line until it reaches a speed of 27 m/s. The vehicle then slows at a constant rate of 1.4 m/s2 until it stops. (a) How much time elapses from start to stop? (b) How far does the vehicle move from start to stop?
Initial speed of the vehicle = V0 = 0 m/s (At rest)
Maximum speed the vehicle reaches = V1 = 27 m/s
Acceleration of the vehicle while speeding up = a1 = 2.4 m/s2
Time period the vehicle speeds up for = T1
V1 = V0 + a1T1
27 = 0 + (2.4)T1
T1 = 11.25 sec
Distance the vehicle travels while speeding up = D1
D1 = V0T1 + a1T12/2
D1 = (0)(11.25) + (2.4)(11.25)2/2
D1 = 151.88 m
Final speed of the vehicle = V2 = 0 m/s (Comes to a stop)
Acceleration of the vehicle while slowing down = a2 = -1.4 m/s2 (Negative as it is deceleration)
Time period taken for the vehicle to come to a stop = T2
V2 = V1 + a2T2
0 = 27 + (-1.4)T2
T2 = 19.29 sec
Distance the vehicle travels while slowing down = D2
V22 = V12 + 2a2D2
(0)2 = (27)2 + 2(-1.4)D2
D2 = 260.36 m
Total time elapsed from start to stop = T
T = T1 + T2
T = 11.25 + 19.29
T = 30.54 sec
Total distance traveled by the vehicle = D
D = D1 + D2
D = 151.88 + 260.36
D = 412.24 m
a) Total time elapsed from start to stop = 30.54 sec
b) Total distance traveled by the vehicle = 412.24 m