Newton’s 3rd Law
For every action there is always an equal and opposite reaction.
The Normal Force
The reaction force exerted plane or the plane on the block depends on the weight of the block, the inclination of the plane and other forces that are exercised on the block.
Friction
Force that opposes the motion of bodies on a surface.
Static friction
Frictional force us sufficient to prevent relative movement between their surfaces
Fs = s N
Kinetic friction
Frictional force acting on an object when it is in motion.
Fk = k N
Dynamic equilibrium Static Equilibrium
F = m a F = 0

Newton’s 2nd law
Alteration of motion (acceleration) is proportional to the force applied; and it goes in the direction where the force is …ver más…

A 100 kg ball is lowered by means of a cable with a downward acceleration of 5 m/s2. What is the tension in the cable?

A 5 kg block m, rests on a frictionless tabletop. A cord attached to it passes over a light frictionless pulley and is attached to a mass m2. (a) What must be the mass m2, such that the system accelerates at 2 m/s2? (b) What is the tension in the cord for this agreement?

A 50 N sled rests on a horizontal surface. A horizontal pull of 10 N is required just to start the sled moving. After motion is started, only a 5 N force is needed to move the sled with a constant velocity. Find the coefficients of static and kinetic friction.
Assume surface where s = 0.7 and k = 0.4. What horizontal force us needed to just start a 50 N block moving along a wooden floor? What force will move it at constant speed?
What force T at an angle of 30° above the horizontal is required to drag a 40 lb chest to the right at constant speed if k = 0.2?
A 60 N toolbox is dragged horizontally at constant speed by a rope making an angle of 35° with the floor. The tension in the rope is 40 N. Determine the magnitude of the friction force and the normal force.
A 120 N concrete block rests on a 30° inclined plane. If k = 0.5, what push P parallel to the plane and directed up the plane will cause the block to move (a) up the plane with constant speed and (b) down the plane with constant speed?
Se empuja un