21-Q21- An electric car starts from rest and accelerates at the rate of 2 m-s2 nbsp- in straight line until it reaches a speed of 20 m-s- Now the car slows at constant rate 1 m-s2 until it stops- Total distance from starts to stop is- nbsp- nbsp- nbsp- nbsp- nbsp- nbsp- -A- 300 m nbsp- nbsp- nbsp- nbsp- nbsp- nbsp- nbsp- nbsp- nbsp- nbsp- nbsp- nbsp- nbsp- nbsp- nbsp- nbsp- nbsp- nbsp- nbsp- nbsp- nbsp- nbsp- nbsp- nbsp- nbsp- nbsp- nbsp- nbsp- nbsp- nbsp- nbsp-B- 200 m- nbsp- nbsp- nbsp- nbsp- nbsp- nbsp- -C- 100 m nbsp- nbsp- nbsp- nbsp- nbsp- nbsp- nbsp- nbsp- nbsp- nbsp- nbsp- nbsp- nbsp- nbsp- nbsp- nbsp- nbsp- nbsp- nbsp- nbsp- nbsp- nbsp- nbsp- nbsp- nbsp- nbsp- nbsp- nbsp- nbsp- nbsp- nbsp-D- 500 m

Dear Student , Vf = at + Vi nbsp; Vf = final velocity (20 m/s) nbsp; a = acceleration (2 m/s2) nbsp; t = time nbsp; Vi = initial velocity (0 m/s) nbs ...

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Byju's Answer

Standard XII

Physics

Finding Average Velocity

21 Q21. A...

Question

21

Q21. An electric car starts from rest and accelerates at the rate of 2 m/s² in straight line until it reaches a speed of 20 m/s. Now the car slows at constant rate 1 m/s²until it stops. Total distance from starts to stop is

(A) 300 m (B) 200 m

(C) 100 m (D) 500 m

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Solution

Dear Student ,
Vf = at + Vi

Vf = final velocity (20 m/s)
a = acceleration (2 m/s²)
t = time
Vi = initial velocity (0 m/s)

20 = 2t + 0
t = 10s

Find the distance as the car accelerates
Xf = 0.5at² + Vt + Xi

Xf = final position
Xi = initial position
Xf = 0.5(2)(10)²
Xf = 110m

Vf = at + Vi

now that the car decelerates, its initial velocity at the time is 20 m/s. When the car stops, its final velocity is 0 m/s
0 = -1t + 20
-20 = -t
t = 20 s

find the distance as it decelerates
Xf = 0.5at² + Vt + Xi
Xf = 0.5(-1)(20)² + 20(20)
Xf = 200 m

the total time is 10 + 20 = 30 s
the total distance is 200 + 110 = 310 m

Regards

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21 ​Q21. An electric car starts from rest and accelerates at the rate of 2 m/s2 in straight line until it reaches a speed of 20 m/s. Now the car slows at constant rate 1 m/s2 until it stops. Total distance from starts to stop is (A) 300 m (B) 200 m (C) 100 m (D) 500 m

21

Q21. An electric car starts from rest and accelerates at the rate of 2 m/s² in straight line until it reaches a speed of 20 m/s. Now the car slows at constant rate 1 m/s²until it stops. Total distance from starts to stop is

(A) 300 m (B) 200 m

(C) 100 m (D) 500 m