I need help on my homework please!?

Question

Sally travels from one city to another. She drives 30.0 min at 80.0 km/hr, 12.0 min at 105 km/hr and 45.0 km/hr. Determine (a) her average velocity in m/s and (b) total distance traveled.

Can someone please tell me how to figure this out?

Answer 1

Whenever you see this kind of problem (where someone is traveling at different speeds during different time segments), you need to figure out the total distance traveled and the total time spent traveling.  Both are very simple.  

To get the total distance, you calculate the distance traveled in each segment, and then add up the distances for the segments.

To get the average velocity, divide the total distance traveled by the total amount of time traveled.

Be careful about the measurement units.

For example:

For the first segment, Sally drove 30.0 minutes at 80.0 km/hr.

In other words, she drove 0.5 hr. at 80.0 km/hr.

So, the distance she traveled was 0.5 hr. x 80.0 km/hr., or 40 km.

Hope this helps.