How to Determine Constant Force Through Slope

Bodies move down slopes, but not as fast as in freefall.

When an object is stationary, the constant force of gravity pulls it downward. When it moves along a slope, this same constant force acts on it. The force driving the object forward, however, is a combination of gravity and the static friction between the object and the slope. The static friction is itself a function of the object's weight. You can calculate the constant vector force moving the object down the slope using trigonometry.

Things You'll Need

• Scientific calculator or computer

Instructions

1. Find the difference between the measure of the slope and 90. If, for example, an object slides down a 30-degree slope: 90 - 30 = 60 degrees.

2. Find the sine of this difference. With this example: sin (60) = 0.866.

3. Multiply this decimal value by the moving body's mass. With a mass of, for example, 20 kg: 0.866 --- 20 = 17.32 kg.

4. Multiply this answer by gravitational acceleration, which is 9.81 Newtons per kilogram: 17.32 --- 9.81 = approximately 170 Newtons. This is the constant force acting on the body in the direction of its motion.

References

• University of Virginia: Weight, Tension, Normal Force, Static Friction
• Tennessee Tech University: Forces

Resources

• Web 2.0 Calculator
• San Diego Miramar College: Torque
• Loras College: Torque and Rotational Equilibrium