Question

A 10-𝑘𝑔 box starting from rest is pulled using a rope that makes an angle of 30o with the horizontal. If it travels a distance of 10 𝑘𝑚 in 2𝑠, what is the magnitude of the force exerted by the rope?

Answer 1

Write the equation that ties together all forces by Newton's second law:

$$ma=F\cos\theta,\\\space\\ F=\frac{ma}{\cos\theta}.$$

The acceleration can be expressed as

$$a=\frac{2d}{t^2}.\\\space\\ F=\frac{2md}{t^2\cos\theta}=58\text { kN }$$