Answer to Question #186397 in Classical Mechanics for somebody

Question

1. A load roller with a weight of 15 N lifts a load of 18 kg. The free end of the rope is subjected to a force of 105 N. Calculate the friction force.
2. The length of one inclined plane is 6 m, the other - 7.2 m. In the first plane the body is raised to a height of 1.5 m, and in the second - to 1.8 m. Which of these planes can win more power?

Answer 1

1. The force of friction is equal to the tension in the free end of the rope:

$$f=T=105\text{ N}.$$

2. For equal mass and materials of the surface, we have different work required to put the mass on the top of the incline:

$$W_1=\mu mgL_1+mgH_1=mg(6\mu+1.5),\\ W_2=\mu mgL_2+mgH_2=mg(7.2\mu+1.8).$$

The first plane, therefore, is more efficient than the second one.