Please help with this physics problem!
a. A 50kg water skier is pulled on a lake by a boat with a horizontal force of 400N. If the wind and current applies another force of 100N at an angle of 30degrees relative to the straight-line direction of the boat, what is the skiers acceleration? B.) what is the acceleration if the wind-current force were in the opposite direction to that in part a).

Hi, this question is concenrning vector addition.

If you draw, on a graph, a line 400 N long in a direction you can call horizontal, then on the end of this draw your 30 degree 100 N force, then the total force felt by the skier is the vector from the start of the 400 N force to the end of the 100 N force.

Hopefully you know how to turn this into a measure of acceleration.

The other part of the question is exactly the same, but with the 100 N force in a different direction.

I hope this helps. Let me know if you need further help.

Well, you can show it using free body diagrams, but the operation you are doing is vector addition, and the easiest way to do that is with a graph...

The other way to do it is to split your forces into vectors along the x and y direction, and add those separately, and then recombine them.
(this uses basic trigonometry)

I'll answer the first part if you want.

I am assuming the wind is blowing against his back at 30 degrees to the boat's vector.
so it is adding 100 cos 30 N to the 400 N of the boat.
There is a further 100 sin 30 N pushing him to one side of the boat.

Using pythagoras we can see the total force is (100sin(30))^2 + (400 + 100cos(30))^2

And you can use F = ma to find his velocity and a little trig to find the direction.

If you need further help please feel free to ask :)