Question

A toy car starts from rest and accelerates at a uniform rate of 4.0 m/s2 for 3.0 seconds. It then
maintains a uniform speed for 12.0 seconds. Finally it takes 6.0 seconds to decelerate uniformly to
rest. Find the total distance travelled and the average speed of the entire trip.
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Answer 1

Answer:

198 m

Explanation:

Case 1: uniform acceleration

u = 0, t = 3 sec, a=4 m/s²

S₁ = ut₁ + 0.5*a*t²

   = 0.5*4*3²

   = 0.5 * 4 * 9

S₁ = 18 m

v = u + a*t

 = 0 + 4*3

v = 12 m/s

Case 2: uniform velocity = 12 m/s

S₂ = v*t

   = 12*12

S₂ = 144 m

Case 2: uniform deceleration

v = 0, u = 12 m/s, t = 6 seconds

v = u + a*t

a = - 2 m/s²

S₃ = u*t + 0.5*a*t²

   = 12*6 - 0.5*2*6²

   = 72 - 36

S₃ = 36 m

Total distance = S₁ + S₂ + S₃ = 18 + 144 + 36 = 198 m