 With a large perpendicular force and a small parallel force, the tendency to slide is very small. An example of this would be a 15 degree slope. The picture shown is a 30 degree slope, which means that although the perpendicular force is still larger than the parallel force the tendency to slide is increasing!

 The pink line in this diagram shows the parallel vector. This is the vector that runs along the plane. This is also the force due to gravity. To solve for this we can use the formula Fgsin=Fg Remember! Keep in mind the force of friction (Ff) when solving for the parallel force.

 The red line shows the perpendicular force. This acts into the plane. Fgcos=Fg In this direction we must consider the normal force (Fn). This is because the object is not falling through the plane, causing a balancing force which pushes back up.

At this 30 degree angle the weight pushing into the ramp is much greater than the weight would be on a 60 degree ramp. This is in reaction to the perpendicular component. However, as the angle is increased the component of the weight in the parallel direction is increased.

 Now, lets say we are using a machine to pull a piano up a large ramp. The machine uses a constant velocity. What must the acceleration be?  This is a trick question because a constant velocity means that there is no acceleration! The piano is being pulled at the same speed the entire time.

1) What happens to the perpendicular component as the angle is increased? 2) What happens to the normal force as the angle is increased? 3) As the angle increases, the frictional force will… 4) If the perpendicular force is large, the tendency to slide is… 5) If there is constant velocity, the acceleration is…

1) The normal force decreases. 2) It will decrease. 3) Change. It will decrease. 4) Very weak. This will become greater as the perpendicular force becomes smaller than the parallel force. 5) There is no acceleration with constant velocity!!!