La Tercera Ley de Newton (Newton's Third Law)

Objectives:

• Observe the magnitude and direction of forces exerted by interacting objects
• Observe the time variation of these forces
• Develop a more detailed explanation of Newton's third law

Key Terms:

• force
• mass
• time
• direction
• magnitude
• acceleration
• velocity
• reaction
• equal/opposite
• equilibrium 

Pre-Lab Discussion:

What is a force?

A force is a push or pull exerted by one object on another. This concept is involved in Newton's third law, which states "for every action, there is an equal, but opposite, reaction." This law deals with the effects of forces on singe objects. 

Consider the following situations before starting the lab:

Procedure: In this lab, we used two Vernier Dual-Range Force Sensors, a LabQuest, the LabQuest app, a Vernier Dynamics Track, and two standard carts.

Part one: String 

A string connects the hooks of the two carts. The carts are pulled apart and produce equal and opposite forces

A string connects the hooks of two carts. Cart 1 is pulled away while Cart 2 is held in place, producing equal and opposite forces. 

Part two: Rubber Band

A rubber band is used to connect the hooks of Cart 1 and Cart 2. When the two carts are pulled apart, they produce equal and opposite forces. 

Extension: 

Would two objects produce equal and opposite forces when collided if one has a different mass? 

This graph depicts Cart 1 (with an increased mass) being pushed against Cart 2. The forces remain equal and opposite.

Part three: Carts

This graph depicts Cart 1 being pushed and Cart 2 is not being touched

This graph depicts Cart 1 being pushed and Cart 2 being held in place

Analysis: 

The goal of this lab was to develop a deeper understanding of Newton's Third Law. The forces we observed in this lab were contact forces (other examples include friction and normal forces). This means that the objects involved had contact interaction with each other. As stated before, Newton's Third Law states that for every action, there is an equal and opposite reaction. By doing this lab, we are able to split it down into:

The size of the forces on the first object EQUALS the size of the force on the second object.
The direction of the force on the first object is OPPOSITE to the direction of the force on the second object. 

Force will always be in a pair: equal and opposite. 

A representation of this idea:

citation: http://patriots-in-motion.wikispaces.com/Newton's+Third+Law

The extension of the lab involved using the two standard carts and the track. As we did this lab, we were faced with the question of whether or not Newton's Third Law would apply if one of the carts had a greater mass. To test this, we simply added some of the weights on to the back of one cart and collided the two and observed the results. The graph under Extension helped us prove this theory to be correct.

BONUS: We made a graph that looks like a cow