How long it takes for a car to catch a truck

[Pioneer98]

Homework Statement

A car traveling 91 km/h is 200m behind a truck traveling 81 km/h . How long will it take the car to reach the truck?

Homework Equations

The Attempt at a Solution

 

[SammyS]

Homework Statement

A car traveling 91 km/h is 200m behind a truck traveling 81 km/h . How long will it take the car to reach the truck?

Homework Equations

The Attempt at a Solution

Hello Pioneer98. Welcome to PF !

What have you tried?

Where are you stuck?

 

[Pioneer98]

I'm actually not even sure where to start. My professor gave us four kinematic equations to memorize and use. I know how to use those, but the things he went over in class are totally different from the online homework.

 

[HallsofIvy]

Motion is always relative. The car is traveling at 10 km/hr faster than the truck. How long will it take to cover 200 m?

 

[Pioneer98]

20 seconds?

 

[SammyS]

20 seconds?

That would be true if car were traveling 10 m/s faster than the truck. Units matter !

Convert 10 km/hr to m/s .

 

[Pioneer98]

10,000 m/hr, 2 7/9 m/s, so it takes 72 seconds for the car to reach the truck. Thanks for the help guys!