Test: Average Velocity & Average Speed - NEET MCQ

A particle moving in a given direction with non-zero velocity cannot have zero speed. In general, average speed is not equal to magnitude of average velocity. However it can be so if the motion is along a straight line without change in direction.

From O to P and back to Q

From O to P and come back to O

The area under the velocity-time graph represents the displacement over a given time interval.

Given: a= 8.5 m
            b=2.5ms⁻²
Position is given as,
x=a+bt² …(1)

At t= 2 s, equation. (1) becomes,
x₂ = a + b(2)²
→ x₂ = a +4 b

Substituting the values in above equation we get,
x₂ = 8.5 + 4 × 2.5
⇒ x₂ = 18.5m

At t= 4 s, equation. (1) becomes,
x₃ = a+b (4)²
→ x₃ = a +16b
Substituting the values in above equation we get,
x₃ = 8.5+16 × 2.5
⇒ x₃ = 48.5m

Displacement from t= 2 s to t= 4 s is given by,
S₂₁ = x₃−x₂
Substituting the values in above equation we get,
S₂ = 48.5–18.5
⇒ S1 = 30m

Time taken by the object to move from x₂ to x₃ is given by,
t′′ = 4−2
⇒ t′′ = 2s 
Therefore, the average velocity of object is given by,
V₂ = S₂ / t′′
Substituting the values we get,
V₂ = 30 / 2
⇒V₂= 15m/s

So, Option (c) is the correct answer.