Balloon Car Experiment
Newton’s First Law of Motion states that when an object is set in motion, it will remain in motion until acted on by an outside force. Theoretically, this could mean you could travel at the same speed forever in one direction, right? The reason we don’t see this happen is because of friction. The force of friction is the resistance to motion that is in the opposite direction of the traveling object. This is why if you roll a ball on the ground it eventually stops. Friction is also the reason you can hold a book, and the reason why you don’t slip when walking! The ground and other solid surfaces can cause friction, called dry friction, but fluids (liquids and gases) like water and air can also cause frictional forces, called fluid friction.
The equation for the force of friction is the following:
Ff = µ * FN
Where Ff is the force of friction, FN is the force normal to the object that is moving, and µ is the coefficient of friction.
The normal force of an object is the force that is perpendicular to the surface of the side of the object that is in contact with the surface that is causing the frictional force. For example, if you have a block moving horizontally on flat ground, the normal force points at a 90° angle out of the ground.
The unit for force is the Newton (named after Sir Isaac Newton), which is equal to 1 (kg) (m) / s2. The coefficient of friction, symbolized by the Greek letter µ (“mu”), is dimensionless, which means it has no units. Dimensionless numbers help scientists, mathematicians, and engineers compare the same characteristic in different objects. In essence, the coefficient of friction describes how easily one object can move over another. Your swimsuit against a water slide has a low coefficient of friction and so does the ice skate blades on ice. We think of these objects as slippery. The rubber of car wheels on the street has a higher coefficient of friction, which is why when there is no force applied...
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