NEETPhysicsElectrostaticsMCQ+4 / −1
A toy car with charge q moves on a frictionless
horizontal plane surface under the influence of
a uniform electric field
. Due to the force q
,
its velocity increases from 0 to 6 m s–1 in one
second duration. At that instant the direction of
the field is reversed. The car continues to move
for two more seconds under the influence of this
field. The average velocity and the average speed
of the toy car between 0 to 3 seconds are
respectively
- A2 m s–1, 4 m s–1
- B1 m s–1, 3 m s–1
- C1 m s–1, 3.5 m s–1
- D1.5 m s–1, 3 m s–1
View written solutionFree
Correct answer: B

Acceleration, a = ${{v - u} \over t}$ = ${{6 - 0} \over 1}$ = 6 ms-2
For t = 0 to t = 1 s,
S1 = $${1 \over 2} \times 6{\left( 1 \right)^2}$$ = 3 m ...(i)
For t = 1 s = to t = 2 s,
S2 = 6.1 - $${1 \over 2} \times 6{\left( 1 \right)^2}$$ = 3 m ...(ii)
For t = 2 s to t = 3 s,
S3 = 0 - $${1 \over 2} \times 6{\left( 1 \right)^2}$$ = -3 m ...(ii)
Total displacement S = S1 + S2 + S3 = 3 m
Average velocity = ${3 \over 3}$ = 1 ms-1
Total distance travelled = 9 m
Average speed = ${9 \over 3}$ = 3 ms-1
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