First slide
The 3 equation for uniform acc
Question

At the instant a motorbike starts from rest in a given direction, a car overtakes the bike, both moving in the same direction as shown in figure. The speed-time graphs for motor bike and car are represented by OAB and CD respectively.

Then,

Moderate
Solution

Distance travelled by motor bike at t = 18 s
s1=12×18×60=540m
Distance travelled by the car at t = 18 s
S2 = 18 x 40 =720m
The separation between motor bike and car at t = 18 s is 720 - 540 = 180 m
Let the separation between them decreases to zero at time t beyond 18 s. Hence
sbike =540+60t and scar =720+40t
scar sbike=0
Therefore,720 + 40 t = 540 + 60 t
Solving we get, t = 9 s beyond 18 s
total time = 18 + 9 = 27 s from the start.
Distance travelled by both sbike + scar = 1080 m

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