# Practice – Find Speed and Velocity

Questions :

A runner ran 8km to the right in 2 hrs. Then he turned back and ran 3 km in 1hr. What are his average speed and velocity for the whole trip?

You started driving north from your home. You covered 100 km in 4 hrs. Then you came back home in 6 hrs. What is your average speed and velocity for this trip?

You walked 8 km east in 3 hrs and then you walked 6 km north in 2 hrs. What are your average speed and velocity for this trip?

A car was going at a speed of 65 km/hr. What is the distance covered by the car after 3 hrs.?

A car was going at a speed of 80 km/hr. How long will the car take to cover 560 km?

Give an example where average speed and average velocity have the same magnitude.

You walked with velocity -4km/hr for 2 hrs and then you walked with velocity +5km/hr for the next 3 hrs. What is your average speed for this trip?

Explanations :

A runner ran 8km to the right in 2 hrs. Then he turned back and ran 3 km in 1hr. What are his average speed and velocity for the whole trip?

Distance covered = 8km + 3km = 11km

Displacement = 8km – 3km = 5km to the right

Average Speed = (Distance covered)/(Total Time) = 11/3 km/hr

Average Velocity  (Displacement)/(Total Time) = 5/3 km/hr to the right.

You started driving north from your home. You covered 100 km in 4 hrs. Then you came back home in 6 hrs. What are your average speed and velocity for this trip?

Distance covered = 100km + 100km = 200km

Displacement = 100km – 100km = 0 km

Total time = 4 hrs + 6 hrs = 10 hrs

Average Speed = (Distance covered)/(Total Time) = 200/10 km/hr = 20 km/hr

Average Velocity  (Displacement)/(Total Time) = 0 km/hr

You walked 8 km east in 3 hrs and then you walked 6 km north in 2 hrs. What are your average speed and velocity for this trip?

Distance covered = 8 km + 6 km = 14 km

Displacement = 10 km

Total time = 5 hrs

Average Speed = (Distance covered)/(Total Time) = 14/5 km/hr

Average Velocity  (Displacement)/(Total Time) = 10/5 km/hr = 2 km/hr

A car was going at a speed of 65 km/hr. What is the distance covered by the car after 3 hrs.?

Average speed = (Distance covered)/(Total Time)

Distance Covered = (Average Speed) x (Total Time)

Distance Covered = 65 km/hr x 3 hr = 195 km ( Pay attention to the unit. “hr” gets cancelled)

A car was going at a speed of 80 km/hr. How long will the car take to cover 560 km?

Average speed = (Distance covered) / (Total Time)

Distance Covered = (Average Speed) x (Total Time)

Total Time = (Distance Covered) / (Average Speed)

Total Time = (560 km) / (80 km/hr) = 7 hrs ( Pay attention to unit. “km” gets cancelled)

Give an example where average speed and average velocity have the same magnitude.

Any 1 directional motion that does not involve a change in direction will have the same average speed and velocity.

You walked with velocity -4km/hr for 2 hrs and then you walked with velocity +5km/hr for the next 3 hrs. What is your average speed for this trip?

Average speed = (Distance covered) / (Total Time)

So you need to find out what is the distance covered.

Distance covered in the first part = 4 km/hr x 2 hr =8 km

Distance covered in the second part =  5 km/hr x 3 hr = 15 km

Total distance covered = 8 km + 15 km = 23 km

Total time = 5 hrs

Average speed = 23/5 km/hr = 4.6 km/hr

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