Roller Coaster Dynamics 2 Lab Summary

Roller Coaster Dynamics 2 Lab Summary Friction, Losses, and Centripetal Force

Losses play an important role in the roller coaster project. The primary losses considered in the project are losses due to friction. Understanding Normal force is important to understand the concept of friction. Try to understand the normal forces the ball encounters on different sections of the track (loops, ramps, flat sections) and the frictional forces that result. Concepts/Definitions: Weight: w  mg The force due to gravity.

Normal Force: A force resulting from two objects ‘pressing’ against each other. This force acts perpendicular to the area of contact (see example below). In the context of the project the normal force often results from the weight force of the ball. A special case to consider is the normal forces the ball experiences when going through a curved section of the track such as a horizontal or vertical loop.

Friction: A force that opposes motion/action. Two forms: static and kinetic.

Static Fsf   s N where  s is the coefficient of static friction and N is the normal force. This is the force encountered when trying to move a stationary object. The ball isn’t stationary in the roller coaster project, it’s rolling along the track, so why care about static friction? Static friction is the force that makes the ball roll along the track instead of sliding along.

Kinetic Fkf  k N where k is the coefficient of kinetic friction and N is the normal force. This is the friction encountered by a moving object.

mv 2 Centripetal Force: F  where m is the mass of the ball, v is the velocity of the ball, c R and R is the radius of the curve. This is a force the ball V experiences when traveling on a curved path such as a turn or a horizontal or vertical loop. This force points towards the center F of the c curve at all points along the curve (see figure at left from lab slides, rotate it mentally). The centripetal force will cause losses since the ball is pressing against the track resulting in friction. Example: Static Friction Assume object mass m resting on a flat surface,

gravity g, and coefficient of static friction  s What is the weight of the ball? W  mg What is the normal force on the ball from the surface? N  W since the surface is ‘flat’ What is the static frictional force right before the object moves on the surface?

Fs   s N   sW   s mg