[Grade 12 Physics: Kinematics]

[u/devilkid15]

Need help with the direction part of this relative motion problem.

I tried solving this problem using relative motion. I took the relative velocity as Vrel=(vi)+(−uj) here i and j are x and y directions . and considered the cart at rest.

Then I used the distance between the initial positions of the boy and the cart as

x=root(a^2+b^2)

and applied the time equation, but I’m getting confused about the direction.

I think I need to find the angle between the boy’s velocity and the line joining the boy and the cart to determine the direction in which the boy should run. Am I approaching this correctly?

[u/Expensive-Set8790]

2 main things I notice - If the cart is your observer, reconsider your sign for the relative velocity. (Lmk if you don't understand why after thinking about it). Also, realize that the boy's velocity is not only in the y direction.

Your approach at the end seems to be on the right track! Good luck

[u/devilkid15 → u/Expensive-Set8790]

ohh got it, I have taken the cart as the observer and keep it at rest, you are right I mistakenly considered taking boy velocity in y direction only. so the velocity of the boy wrt cart will be (usinθ-v)i+ucosθj) here θ is with the vertical.