Two cars start from rest at a red stop light. When the light turns green, both c

Question

Two cars start from rest at a red stop light. When the light turns green, both cars accelerate forward. The blue car accelerates uniformly at a rate of 5.6 m/s2 for 3 seconds. It then continues at a constant speed for 7.6 seconds, before applying the brakes such that the car Two cars start from rest at a red stop light. When the light turns green, both cars accelerate forward. The blue car accelerates uniformly at a rate of 5.6 m/s2 for 3 seconds. It then continues at a constant speed for 7.6 seconds, before applying the brakes such that the car

Explanation / Answer

1)
v= u + a t

=0 + 5.6*2.1

v= 11.76 m/s

2)

velocity after 3 sec of acceleration

v= 0 + 5.6 * 3

v= 16.8 m/s

it travels in constant motion after

so, v= 16.8 m/s afte 7.4 sec

3)

distance travelled in first 3 sec = ut + 0.5at^2

= 0 + 0.5 * 5.6 * 9 = 25.2 m
distance in next 7.6 sec = v* t=7.6 * 16.8= 127.68 m
Total distance= 152.88 m

4)

v^2= u^2 + 2 as

0= 16.8^2 -+2 a * 173.8

a= -282.24/2*173.8

a=-0.812 m/s^2

The deceleration of car after brakes are applied is 0.812 m/s^2

5) v=u + at

t= 16.8/0.812

t=20.69 sec

Total time = 3 + 7.6 + 20.69 = 31 . 29 sec

6)

Total distance= 152.88 + 173.8 =326.68 m

s= ut + 0.5 a T^2

326.68= 0 + 0.5 a 31.29^2

a= 326.68/489.53

a=0.667 m/s^ 2

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