Physics Question (speed/Velocity)?

Question

A car traveling 88km/h is 110 m behind a truck traveling 75km/h.
How long will it take the car to reah the truck?

I dont understand how to arive at the answer. Can someone show me HOW to do it? Thank you

Answer 1

the relative velocity of the car with respect to the truck is:
88km/h - 75km/h = 13km/h

How long does it take to travel 110m at 13km/h?
13km/h * 1000m/km * 1h/3600s = 3.61m/s

110m / 3.61m/s = 30.462seconds.

Answer 2

The difference in velocities between the car and the truck is 88 - 75 = 13 km/h.

So, if the car is closing on the truck at a (relative) velocity of 13 km/h, how long will it take to cover the 110 m (or .11 km) between itself and the truck. Since
distance = velocity * time it's pretty easy to see that
t = d/v = .11 km/13 km/hr = .00846 hours.

Now that's a kind of an awkward way to express time. But, if you remember that one hour is equal to 3600 seconds (60 minutes/hr times 60 s/minute), then
.00846 hrs * 3600 s.hr = 30.456 seconds.

HTH ☺


Doug

Answer 3

First, count the difference in the velocity of the car and the truck:

88-75=13km/h
=13*1000/(60*60)
=3.611m/sec

that means the car will move 13 km/h@3.611m/sec relative to the truck.

the distance to go is 110m, so the time for the car to reach the truck is:
110/3.611 = 30.46 seconds

Answer 4

first off, change km/hr to m/s
88km/hr => 24.44m/s
75km/hr => 20.83m/s


X= Vt + X0
let the truck be the reference point. The car is 110m behind, that means the car is -110m away from the truck

X(car) = 24.44t - 110
X(truck) = 20.83t

when the car catches the truck, their distances and time will the the same. We set the two equation equal to each other.

24.44t - 110 = 20.83t
3.61t = 110
t= 30.47s

the car will catch the truck in 30.47s