Two forces of magnitudes \(80 N\) and \(60 N\) act on a \(5 kg\) object. If the angle between the two forces is \(120^{\circ}\), the acceleration of the body is ____________
A. \(14.4 m / s ^{2}\) B. \(20.0 m / s ^{2}\) C. \(11.9\) \(m / s ^{2}\) D. \(16.7 m / s ^{2}\)
Correct Answer: A
Explanation
Using cosine rule, \(R^{2}=60^{2}+80^{2}-2 \times 60 \times 80 \cos 60^{\circ}\) \(R^{2}=3600+6400-9600 \times 0.5\) \(R^{2}=10,000-4800=5200\) \(R=72.11 N\) from Newton's second law, \(f_{\text {net }}=\) ma or \(R=m a\) \(a=\frac{R}{m}=\frac{72.11}{5}=14.4 m / s ^{2}\)
