Question

A car starts from rest and accelerates uniformly for 10s to a velocity of 36km/hr .It then runs at constant velocity and finally comes to rest in 50m with constant retardation . Find The total acceleration, time taken and retardation of car.

Answer 1

I. Accelerating part

u = 0
v = 36 km/hr
v = 36×5/18 m/s
v = 10 m/s
t = 10 s
a = (v - u)/t
a = (10 - 0)/10
a = 1 m/s^2
s = ut + 1/2at^2
s = 0 + 1/2 × 1× 100
s = 50 m

II. Constant velocity or zero acceleration

v = 10m/s

III. Retarding part

u = 10m/s
v = 0
s = 50 m
v^2 - u^2 = 2as
0 - 100 = 2a×50
a = -100/100 = -1 m/s^2
t = (v-u)/a
t = (0-10)/(-1)
t = 10 s

I think question is incomplete. Data is insufficient to find the total time taken.
Acceleration is 1 m/s^2
and retardation is -1 m/s^2.


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