Force is defined as a push or pull acting on an object. Forces include gravity, friction, and applied force. Force causes changes in the speed or direction of motion. These changes are called acceleration.

Learning the Formula. Multiply mass times acceleration. The force (F) required to move an object of mass (m) with an acceleration (a) is given by the formula F = m x a. So, force = mass multiplied by acceleration.

Friction when an object slides along a surface. Direction is opposite the object’s sliding direction and is parallel to the contact surface.

As shown in the diagram, there are always at least two forces acting upon any object that is positioned on an inclined plane – the force of gravity and the normal force.

1. The normal force of an object placed on a sloping surface is always perpendicular to the surface.
2. mgsinθ
3. Take g = 9.8ms-2.
4. (a) Σ F = ma = mg sin θ where mg sin θ is the component of the force parallel to the slope.

This supporting force acts perpendicular to and away from the surface. It is called a normal force, and it also goes by the name “apparent weight.” When objects rest on a non-accelerating horizontal surface, the magnitude of the normal force is equal to the weight of the object: N=mg.

Putting “Friction on an Incline” in Conceptual terms: With an incline, the force of gravity is not perpendicular to the surface. As the angle of the incline is increased, the normal force is decreased, which decreases the frictional force.

Resultant force F = 3 N + 2 N = 5 N to the right. The resultant force is 5 N to the right. Two forces that act in opposite directions produce a resultant force that is smaller than either individual force. To find the resultant force subtract the magnitude of the smaller force from the magnitude of the larger force.