Question

14.2. A motorist takes 10 seconds to cover a distance of 20 m and 15 seconds to cover a distance of
40 m. Find the uniform acceleration of the car and the velocity at the end of 15 seconds.
[0.267 m/s?, 4.7 m/s]​

Answer 1

Answer:

Explanation:

I assume initial speed of motor is u m/s,  then the motor has travelled a distance 20 m at first 10 s

and moved a distance 8 m in next 15 seconds.

 

I also assume it is required to get acceleration a and speed after 15 seconds staring from initial time.

 

distance S travelled in first 10 s  is given by, S = ut+(1/2)at2;   20 = 10u +(1/2)a×100   or u + 5a = 2 ..............(1)

 

speed v after 10 s is given by v = u+at ;  v = u+10a

 

if 8 m distance is travelled in next 15 s, then  8 = (u+10a)15 + (1/2)a×225    or    15 u + (525/2)a = 8 ..................(2)

 

By solving eqn.(1) and eqn.(2), we get acceleration  a = -44/375 m/s2   and  u = 194/75 m/s

 

speed after 15 seconds,  v = (194/75) -(44/375)×15 = 62/75 m/s   = 0.83 m/s

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