Question

Bob and joe have a class together at Kensington college. They leave the class at the same time. Bob goes to the library at 4 miles per hour, joe heads to the exact opposite direction at 2 miles per hour. How long will it be before the classmates are 2 miles apart .

Answer 1

Solution

For this case we can create the following schema

We can use the definition of distance:

x= vt

We can find the relative velocity:

$V_{\text{rel}}=4-2=2\frac{mi}{hr}$

And the distance between both is required to be 2 mi so then we can find the time like this:

$t=\frac{x}{v_{\text{rel}}}=\frac{2mi}{\frac{2mi}{hr}}=1hr$

Then the answer is:

1 hr