Question

1.) Emily leaves her physics book of mass 1 kg on the top of the table that is inclined at an angle of 20°. What is the acceleration of the book if the coefficient of kinetic friction between the book and the inclined plane is 0.3

2.) A boy pulls a toy cart of mass 2 kg with a force of 3 N at an angle of 60° with respect to the horizontal road. What is the acceleration produced by the cart?
3.) A man pulls a suitcase of mass 15 kg with a force "F" inclined at an angle of 60° to the horizontal. The frictional force between the floor and the wheels of the suitcase is 10 N. What is the force required to produce an acceleration of 0.1 m/s2 on the suitcase?
4.) The net force on a sailboat is 252 N, while the wind exerts a force of 325 N. What is the water-resistant force acting on the sailboat?
5.) A parachutist of mass 75kg descends with an acceleration of 8 m/s2. What is the upward force exerted by the air on the parachutist?

Answer 1

In all the problemas we consider the gravity acceleration equals to 10 m/s2

1) Applying the 2nd law of Newton:

1x10xsin(20°) - 0.3x10xcos(20°) = 1xa

a = 0.6011 m/s2

2) Applying the 2nd law of Newton:

3 - 2x10xsin(60°) = 2xa

a = -7.1602 m/s2 (The negative sign means that the cart is going down)

3) Applying the 2nd law of Newton:

F - 15x10xsin(60) - 10 = 0.1x15

F = 141.4038 N

4) Applying the 2nd law of Newton:

Net force = 325 - F = 252

F = 73 N

5) Applying the 2nd law of Newton:

75x10 - F = 75x8

F = 150 N