- #1
Woolyabyss
- 143
- 1
Homework Statement
Two straight roads intersect at point O and cross at an angle Θ to one another, such that tan Θ = 3/4.Two cars, A and B are traveling towards O on these roads,A at 5 m/s and B at 8 m/s
At a certain moment.A is 100 m from the junction and B, on the other road, is 200 m from the junction. Find
(i)the time at which A reaches O
(ii) The distance between A and B at this time.
(iii) The magnitude and direction of the velocity of A with respect to B
(iv) The shortest distance between them.
(v)the time at which they are nearest to one another
(vi)the time when they are equidistant from O
Homework Equations
Vab = Va - Vb
The Attempt at a Solution
I got every part except (vi)
(i) 100/5 = 20 seconds
(ii) 200 - 8(20) = 40m
(iii) Vab = ( -5(4/5)i -5(3/5)j ) -(-8i) = 4i -3j m/s
|Vab| = 5m/s
inverse tan 3/4 = 36.87 degrees south of east
(iv)
40(sinΘ) = 40(3/5) = 24 m = shortest distance
(v)
Pythagoras theorem (40^2 -24^2)^(1/2) = 32m
32/5 =6.4 seconds
20 + 6.4 = 26.4 seconds
(vi)
This is the part I am stuck on.I know I need the distance from O when they are equidistant but I just can't seem to think of any way that I could get none of the examples in my book
covered this any help would be appreciated.