Question

5 The diagram shows an experiment to measure the force exerted on a ball by a horizontal air flow.

The ball is suspended by a light string and weighs 0.15N.
The deflection of the string from vertical is 30°.
What is the force on the ball from the air flow?

A 0.075N B 0.087N C 0.26N D 0.30N

Answer 1

The answer is B

Answer 2

But howw??

Answer 3

That's easy. There is tension in the string and it should balance both-the weight of the string and the force due to the air flow. You should now be to draw the following diagram.
F is the force due to the air. W is the weight.
Balance the forces in the horizontal and vertical directions

Tsin30 = F
Tcos30 = W

Divide these two equations and solve for F (W is given).