Net Force

Unbalanced Forces Newton’s Second Law requires a net force. One or more forces act on an object Forces are vectors that can be added Add all vector forces acting on a object. If the sum is zero – equilibrium. If the sum is not zero – net force.

Force Vectors Force is a vector. A block sliding on an inclined plane has forces acting on it. We know there is a force of gravity and normal force. m q

Force Diagram Draw the forces acting on the block. The force of gravity points down with magnitude Fg=mg. The normal force points away from the surface of the inclined plane. m q

Force Diagram Draw components of the forces so the vectors can be added. The coordinates should point along the surface. The normal force is unknown The motion will be along the surface The components of Fg are compared to the surface. m q

Net Force The block stays along the plane. Solve for the normal force: No motion or acceleration away from the surface No force in that component Solve for the normal force: Solve for the net force: m q

Motion from Force The net force causes the block to accelerate. The amount of acceleration is force divided by mass. This is a constant acceleration moving the block. m q

Inclined Plane Pushing a block up an incline is easier than lifting. To get constant velocity a force equal to the downward acceleration must be applied. m q next