Question

A man walks 7km in to two hours and 2 km in 1hour in the same direction.

(a)What is the man's average speed for the whole journey?

(b)What is the man's average velocity for the whole journey?​

Answer 1

Given:

• Man walks 7 km in 2 hrs
• Then he walks 2 km in 1 hour

To find:

• Average speed
• Average velocity

Solution:

• Speed is a scalar quantity and velocity is a vector quantity.
• Speed = Total distance / Total time
• Velocity = Total displacement / Total time
• Velocity takes into consideration direction of travel too.
• Total distance travelled by man = 7 km + 2 km = 9 km.
• Total time taken = 2 + 1 = 3 hrs
• Average speed = 9/3 = 3 km/hour.
• Average velocity will be the same as average speed in this case since there is no direction change mentioned.
• Hence, we consider no change in direction throughout the travel
• Therefore Total Displacement = Total Distance
• Hence, average velocity = average speed = 3 km/hour.

Answer:

• Average speed = 3 km/hr.
• Average velocity = 3 km/hr.

Answer 2

Answer:

Given: A man walks 7 km in 2 hrs

Later he walks 2 km in 1 hour

We need to find the average speed and average velocity

Solution:

We know that

Speed = Total distance / Total time

Total distance travelled by man = 7 km + 2 km = 9 km

Total time taken = 2 + 1 = 3 hrs

Average speed = 9/3 = 3 km/hour.

Velocity = Total displacement / Total time

Average velocity will be the same as average speed in this case since there is no direction change mentioned.

Therefore Total Displacement = Total Distance

average velocity = average speed = 3 km/hour.

Hence

Average speed = 3 km/hr.

Average velocity = 3 km/hr.