Question

Two cars X and Y start from two points separated by 75 m. Y which is ahead of X. starts from rest with acceleration of 10 m/s2 and X starts with uniform velocity of 40 m/s . They meet each other twice in their journey. Find the time gap between their meetings.

Answer 1

Explanation:

for car x velocity is uniform ,therefore acceleration of car x is zero.for car Y initial velocity is zero because it starts from rest.

Answer 2

Hence the time gap between their meeting will be 2s

Explanation:

We know that

• Initial speed of Y = 0
• Acceleration of Y = 10 m/s/s
• Initial speed of X = 40 m/s
• Acceleration of X = 0

Now by the concept of relative motion we have

d = v (rel) t + 1 / 2 a rel t^2

75 = 40 t + 1 / 2 (-10) t^2

5 t^2 - 40 t + 75 = 0

t^2 - 8 t + 15 = 0

(t - 3)(t - 5) = 0

t = 3 s , 5 s

Δt = 5 s - 3s = 2s

Hence the time gap between their meeting will be 2s