Newton's Laws

Newton's Three Laws of Motion

Newton's Three Laws:

First Law: An Object at rest or in motion will continue to be that way unless acted upon by an unbalanced(net) force.

Second Law: Force=(Mass)(Acceleration)

Third Law: For every action there is an equal and opposite reaction

Hover Disc Lab

Purpose: The purpose of this lab was to help us better understand Newton's First and Third laws of motion.

Background: Before starting this lab we learned about all of the forces in nature that can explain and predict what we observe in the universe.

• • Gravitational - Fg - two objects have mass
  • Normal - FN - electrons on the surface of atoms repel
  • Friction - Ff - electrons on the surface of atoms are shared
  • Tension - Ft - electromagnetic bonds are stretched (rope)
  • Spring - Fs - electromagnetic bonds are stretched/compressed (spring)
  • Buoyancy - FB - fluid molecules repel on/in liquid

Procedure: We completed this experiment in total of 10 trials. For the first few trials, we turned the fan on to eliminate friction between our object and the ground. Then for the last few trials we  turned of the fan, making Friction for a factor in our experiment. We did a variety of things, but mostly we either had person 1 or 2 push the disc or stop the disc, or we just let the disc move at a constant speed by itself.

Data: We used two different types of diagrams to interpret our data, Interaction diagrams and Free Body diagrams. Interaction diagrams allow us to see the different types of forces between all of the the objects in our experiment, and a free body diagram allows us to see the forces acting on one of our objects...in this case our disc.

Hover disc is ON. Disc is at rest. Disc had not been pushed.

Hover disc is OFF. Disc is being pushed by person 1.

Hover Disc is ON. Disc is being caught by person 1.

Conclusion: From all of this data, we are able to prove Newton's first law, that an object at rest or in motion will continue to be that way unless acted upon by an unbalanced(net) force. We also prove Newton's third law, that for every action there is an equal and opposite reaction(using the same force). We observe this when the hand stops the disc from moving. Both are exerting normal force, but they are moving in opposite directions.

Real World Connection: Air Hockey

Air hockey is a perfect example of Newton's First Law.In the game of air hockey you have a puck, handles, and a table. The air coming up from out of the table eliminates the friction between bot the puck and your handles. If you were to leave the puck and handles on the table while the table was on, the puck and handles would continue moving at a constant speed forever(or at least until the table's batteries ran out). When you hit the puck with the handle though you are creating a net(unbalanced) force, therefore causing the puck to accelerate.

Fan Cart Lab

Purpose: The purpose of this las was to better understand Newton's Second Law and the relationship between mass, force, and acceleration.

Background:  1) Acceleration is a change in velocity over time

                         2) Acceleration is the slope in a velocity 

Procedure: We had a track with a sonic range finder on one end and a force probe with a metal ring attached to it on the other end which was hooked up to the computer. We completed a total of 5 trials, and for each trial we increased the mass of our cart by adding brass masses.

Data: In order to find the acceleration of our fan cart we measured the slope, because acceleration= the slope. We also analyzed our data using liner fit(y=mx+b) because we were finding the slope.

Here are two examples of our graphed data:

Mass=.5kg - Acceleration=.3773m/s^2

Mass=1.3kg - Acceleration=.1372 m/s^2

After we got the results for all 5 trials, we tried to derive an equation from our data.

Equation Time!

Fnet= m(a)

• F= net force
• m=mass
• a=acceleration 

Analysis: From our data we were able to conclude that net force equals mass times acceleration, and that mass and acceleration are inversely proportional (as the mass increases the acceleration decreases). We also were able to understand the concept of net force, and that unless an object has a net(or unbalanced) force, the object will not accelerate.So an object's acceleration depends on it's mass and the net force it experiences.

Real World Connection:

This lab can be connected to something a lot of us do regularly, and one of my absolute favorite things to do...grocery shopping. If we were to push our cart several times(with the same amount of force) and each time add more mass(more food) to our shopping cart, as our cart's mass increased, our acceleration would decrease each time.