Question

If a body travels from A to B, at 40m/s and from B to A at 60m/s, what is its average velocity

Answer 1

Answer :

Given -

• Body travels from A to B at 40 m/s speed.
• Then, the body travels B to A at 60 m/s.

To Find -

• Average Speed ?

Solution -

The Displacement of the motion will be 0 as the final point and the initial point of the motion is same.

Let the Distance travelled by the body from A to B = x.

So, the Total Distance travelled = 2x.

Now, Time taken to travel from A to B = x/40 s.

And the time taken to travel from B to A = x/60 s.

Hence, Total Time = x/40 + x/60 = (3x + 2x)/120 = 5x/120 s.

Now, Average Velocity = Total Displacement/Total Time

So, Avg. Velocity = 0/(5x/120)

⇒ Avg. Velocity = 0 m/s

Hence, The Average Speed of the body is 0 m/s.

Answer 2

Answer :

Given that a body travels from A to B at 40 m/s and from B to A at 60 m/s.

We have to find average velocity of body.

Let the distance b/w A to B be dm.

Here body travels from A to B at 40 m/s and from B to A at 60 m/s.

We know that,

→ Speed = Distance/Time

→ 40 = d/Time

→ 40 × Time = d

→ Time₁ = d/40 h

Now again,

→ 60 = d/Time

→ 60 × Time = d

→ Time₂ = d/60 h

Now we can see that initial position of body remains same. I.e. body travels from A to B first. Then it travels from B to A.

Means that initial position of body is A i.e. same.

We know that, displacement is shortest distance covered b/w two different points.

When initial position of a body is same then displacement = 0

→ Total displacement = AB - BA

→ Total displacement = d - d

→ Total displacement = 0

Now we know that,

→ Average velocity = Total displacement/Total time

→ Average velocity = 0/(d/40 + d/60)

→ Average velocity = 0/{(3d + 2d)/120}

→ Average velocity = 0/(5d/120)

→ Average velocity = 0 m/s

Average velocity of body = 0 m/s [Ans.]✓