Elevating the Elevation of Elevators: An Evaluation on Elevators (Slimy Chemistry)

Objectives: 

• How does the data you collected relate to your answers to the Pre-Lab Questions?
• Can you use your data, observations, and experience to derive a formula to determine the acceleration of the elevator? (Think about the N2L and what your force probe or plate is actually measuring…)
• How does this lab extrapolate to amusement park rides like “Scream” or to other “weightlessness” experience like riding the “Vomit Comet?”

Key Terms:

• normal force
• elevation
• tension
• gravity
• free-body diagram 
• acceleration

Pre-Lab Discussion:

1. When do you “feel heavier?”

I "feel" heavier when the elevator is going up. 

2. When do you “feel lighter?”

I "feel" lighter when you are going down. 

3. When do you “feel normal?”

I "feel" normal when then elevator is not moving. 

4. Why do you think your perception of your weight changes?

I think the perception of the changing weight is due to a change in force.

Procedure:

What we used: A LabQuest, a Force Plate, and the elevator pass.

1. We hacked in to the elevator

2. Placed our Force Plate in the elevator, had someone stand on it and stay still the entire experiment

3. Started the 20 second LabQuest collection and sent the elevator up (first floor to third floor):

First floor to Third floor

4. After recording this data, we started data collection again and sent the elevator down:

Third floor to First floor

Analysis:

As a person stands still on a scale, the Normal force will equal Gravitational force in a free body diagram like this:

This photo represents:

F = 0

Fn - mg = 0

Fn = mg

If this person is put in an elevator, the Normal force begins to change as the elevator travels up and down. 

While the elevator is traveling upwards, the normal force must increase in order to achieve an acceleration upwards. This addition to the normal force is defined as ma, or mass * acceleration. The equation will now look like Fn = mg + ma, meaning the normal force is made of the gravitational force (mg) and the net force (ma) of the person. 

As the elevator begins to travel downwards, the normal force will decrease in order to decelerate as it opposes the force of gravity. The net force on this elevator becomes negative because the acceleration, or a, in ma will become negative. The equation will now look like Fn = mg - ma, meaning the normal force is decreased.

When the elevator has reached constant velocity, this means the acceleration of the elevator is 0m/s^2, which will produce a scenario that is equal to an elevator that is not moving. The equation for this situation is Fn = mg. 

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

Atwood's Machine Lab?????

Objectives: 

1. Ask questions about how the factors of this lab will make a system move

2. Apply the laws of motion to the Atwood's Machine

Key Terms:

• inertia
• equilibrium 
• disequilibrium 
• velocity
• acceleration

Pre-Lab Discussion

What are the laws of motion? What does each law state?

The laws of motion refer to Newton's laws of motion. These laws describe the relationship between an object, the forces acting upon them, and the motion they perform in response to these forces. The first law describes inertia. The second law is the relationship between acceleration, mass, and force. The third law states describes equal and opposite physical reactions. 

When specifically discussing Newton's First Law, this law states that if the net force on an object is zero, then the object is at rest or moves with a constant speed with no change in its direction. 

What We Used:

• stand
• clamp
• PhotoGate
• pulley wheel
• two 50g hook weights
• various weights

Video: Change in Force

Change in Force - Constant Velocity

Change in Mass - Acceleration

Essential Questions: 

1. What are the variables that determine a system's state of motion (constant velocity vs. constant acceleration)?

The variables the determine a system's state of motion (constant velocity vs. constant acceleration) are FORCE and MASS. 

2. What happens when the total mass of a system is kept constant, but the net force is varied?

When the total mass of a system is kept constant and the net force is varied, the system experiences an increase in acceleration. This principle adheres to Newton's Second Law, which states that an object will accelerate if the net force does not equal zero. As long as you have constant mass, acceleration will increase with force. These two factors are proportional, meaning if force is doubled acceleration is doubled. This can be expressed in the equation:

a = F/m

Let a = acceleration

Let f= force

Let m = mass

This equation can be manipulated in to:

F = am

and

m = F/a

3. What happens when the net force on a system is kept constant, but the total mass is varied?

When the net force on a system is kept constant, but the total mass is varied, the acceleration of the system decreases. The principle also applies to Newton's Second Law, which states that an object will decelerate if the net force is 0 but the mass increases. Similarly to question two, this is due to the relationship between acceleration, force, and mass.