A motorcyclist started a race from START line and from rest, and accelerated with the acceleration of 2 m/s2 for 7 seconds. Then he increased the acceleration to 4 m/s2 and went with that acceleration for 8 seconds. What was the racer’s position from the START line after 7+8 seconds from the start of the race?

289 m .

Explanation:

s = ut + 1/2 at² , u is initial velocity , t is time , a is acceleration and s is distance covered .

For t = 7 s

s = 0 + 1/2 x  2 x 7²

= 49 m

velocity after 7 s

= a x t = 2 x 7 = 14 m /s

for next 8 s , initial velocity u = 14 m /s

S = ut + 1/2 at²

= 14 x 8 + 1/2 x 4 x 8²

= 112 + 128

= 240 m

Total displacement in 7 + 8 s

= 49 + 240 = 289 m .

i am pretty sure it is c because when people are closer together, they cannot move as freely. picture being in a mostly full elevator, for instance. the people are right next to you, and you can barely move.