Browsing as Guest. Progress, bookmarks and attempts are disabled.
Log in to track your work.
June 2015 p41 q2
3639
Three horizontal forces of magnitudes F N, 63 N and 25 N act at O, the origin of the x-axis and y-axis. The forces are in equilibrium. The force of magnitude F N makes an angle θ anticlockwise with the positive x-axis. The force of magnitude 63 N acts along the negative y-axis. The force of magnitude 25 N acts at tan-1 0.75 clockwise from the negative x-axis (see diagram). Find the value of F and the value of tan θ.
Solution
Resolve the forces into their components. For the force of 25 N, the angle with the negative x-axis is tan-1 0.75, which gives \cos \theta = 0.8 and \sin \theta = 0.6.
The components of the force F are:
\(F_x = F \cos \theta = 25 \times 0.8 = 20\)
\(F_y = F \sin \theta = 63 - 25 \times 0.6 = 48\)
Using equilibrium conditions, \(F = \sqrt{F_x^2 + F_y^2}\) or \(\tan \theta = \frac{F_y}{F_x}\).