Forces on an Incline Computer Lab

This lab manual is prepared for an open source simulation published at http://www.thephysicsaviary.com/Physics/Programs/Labs/ForcesOnInclineLab/index.html

Theory

a car moving downhill with the forces' diagram

Figure 1. Forces on an incline.

On an incline, the weight on any object is decomposed into its parallel and perpendicular component.

The parallel one, unless equilibrated by some other force, causes the down the hill acceleration.

The perpendicular one is equilibrated by the incline plane; hence, there is no motion in the perpendicular direction.

The parallel component of the weight vector pulls an object down but it is not the only force affecting on the object. Between any two surfaces there is a frictional force that is always opposite to the direction of motion. The object on the incline may be in motion only if the pull-down force is greater than the frictional force that holds it in place. That is explained in the video.

As explained in the video, objects slide down the incline when the parallel component of weight (mg sin θ) is at least equilibrates the frictional force (Figure 2).

Figure 2. Forces in Equilibrium

Both forces are in equilibrium for a specific angle.

Experimental Procedure

Objectives

The objective of this lab is to investigate the forces acting on a cart on an inclined plane as a function of the angle of incline. Specifically, finding the angle at which the parallel component of the weight on the inclined plane (mg sin θ) is equal to the frictional force (f = μ mg cos θ).

online Simulation

The simulation allows adjusting friction coefficients, block mass, and gravitational field (Figure 2). After choosing the desired values at the dashboard (step 1), click to change angle (step 2). The plane will rise automatically. When the block starts moving, click to freeze angle (Figure 2, step 3). Repeat for various masses of the block and various coefficients. Take notes.