Net Force

1. Net Force

2. 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.

3. m q 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.

4. 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.

5. 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.

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

7. 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.

8. 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. next