Question

a body travel 200cm in the first 2 second 220 cm in the next 4 second with deceleration. The velocity of the body at the end of the 7th second is

a)5 cm/s
b)10 cm/s
c)15 cm/s
d)20 cm/s

Answer 1

We are assuming that the body is under uniform acceleration here. Then, the total distance d travelled after the first t seconds is given by

d=ut+12at2d=ut+12at2

Where u is the initial velocity and a is the acceleration. We put the values of these quantities for the first 2 seconds:

200=2u+2a200=2u+2a

where u is in cm/s and a is in cm/s/s.

Then at the end of 6 seconds, the total distance travelled is 200+220 = 420 cm. So,

420=6u+18a420=6u+18a

Upon solving, this gives u = 115 cm/s and a = -15 cm/s/s.

So velocity at the end of 7 seconds is given by:

v=u+atv=u+at

= 115 - 105 = 10 cm/s