Why Was Newton So Important?

Explain the movement of objects by applying Newton's three laws.


Newton’s 1st Law

You will complete all of the following stations, but you do not have to complete the stations in any particular order. There should be two to three sets of each station, and you should complete this activity in pairs:

Cardinal Station

Materials: Two masses, two strings

Set the station up so that there’s a string attached to the metal rod, connected to a mass. There should be another string from the top mass, connected to a second mass.

  1. Pull the bottom string slowly until both masses fall. Which string broke?
  2. What was at rest before the activity (use the materials to help)?
  3. What was in motion during the activity?
  4. Sketch what happened using squares to represent the masses and arrows to represent motion.
  5. Do it again, but this time pull the bottom mass as quickly as you can. Which string broke?
  6. What was at rest before the activity?
  7. What was in motion during the activity?
  8. What was at rest after the activity?
  9. Sketch what happened using squares to represent the masses and arrows to represent motion.
  10. Describe the inertia for the top mass in each situation. Did the top mass tend to stay in motion or remain still? Your response should include at least two sentences to be complete.

Prospect Station

Materials: Paper, mass

Set up the paper and mass so that the short side of the paper is hanging off the table, and 2/3 of the paper is hanging off the table (it will be marked with an “X”). Place the mass on top of the paper that is still on the table (marked with an “M”).

  1. Slowly pull on the paper. Before the weight falls off the table, what’s happening?
  2. What was at rest before the activity (use the materials to help)?
  3. What was in motion during the activity?
  4. Sketch what happened using a square to represent the mass and an arrow to represent motion.
  5. Set it up again, but this time, snap the paper down towards the floor as fast as you can. What happened?
  6. What was at rest before the activity?
  7. What was in motion during the activity?
  8. What was at rest after the activity?
  9. Sketch what happened using a square to represent the mass and arrows to represent motion.
  10. Describe the inertia for the mass in each situation. Did the mass tend to stay in motion or remain still? Your response should include at least two sentences to be complete.

Euclid Station

Materials: 5 books

Set up 5 books on top of each other with the second book from the bottom slightly jutting out from the rest by about 3 inches.

  1. Slowly pull the second book out from the stack. What’s happening?
  2. What was at rest before the activity (use the materials to help)?
  3. What was in motion during the activity?
  4. Sketch what happened using squares to represent the books and arrows to represent motion.
  5. Snap the second book out quickly from the stack. What happened?
  6. What was at rest before the activity?
  7. What was in motion during the activity?
  8. What was at rest after the activity?
  9. Sketch what happened using squares to represent the books and arrows to represent motion.
  10. Describe the inertia for the mass in each situation. Did the books on top of the second book tend to stay in motion or remain still? Your response should include at least two sentences to be complete.

Shaw Station

Materials: Index card, cup, penny, ruler

Near the edge of the table, set up the index card on top of the cup, and balance the penny on the index card. Place a ruler on the side of the table so you can knock out the index card without hitting the cup. You may have to practice this a few times.

  1. Slowly pull the index card off of the cup. What’s happening?
  2. What was at rest before the activity (use the materials to help)?
  3. What was in motion during the activity?
  4. Sketch what happened using arrows to represent motion.
  5. Quickly snap the ruler against the index card so it hits only the index card and not the cup. What happened?
  6. What was at rest before the activity?
  7. What was in motion during the activity?
  8. What was at rest after the activity?
  9. Sketch what happened using arrows to represent motion.
  10. Describe the inertia for the penny in each situation. In which direction did the penny tend to move and why? Your response should include at least two sentences to be complete.

Conclusions

  1. What is inertia? Respond in your own words.
  2. What determines whether something remains still or starts to move?
  3. What is the relationship between mass and inertia? In other words, what influence does mass have on the inertia of an object?


Moving With Inertia

The next time you take a trip in a vehicle (bus, train, car, etc.), note what it feels like when you are:

  1. Accelerating
  2. Decelerating (slowing down)
  3. Traveling a constant speed (when there is no acceleration or deceleration)
  4. Changing direction but not changing speed

For each case, write down:

  1. Where your weight is shifted, if at all
  2. In terms of inertia, why this is happening.

Also, for #4, is your velocity changing? Why or why not?

Speed and Velocity

Speed is calculated by dividing distance by time. We often measure speed in miles per hour, feet per second, meters per second or kilometers per hour. For this activity, we will be measuring speed in feet per second, so we will be using feet as our unit of distance and seconds as our unit of time.

  1. Get a partner, a ball and a stopwatch or timer. Given that each floor tile in the science room is one foot wide (and long), calculate the average speed of a rolled ball three times for these distances (s = d/t ):
    1. 10 feet
    2. 20 feet
    3. 30 feet
Distance (ft) 1st Trial 2nd Trial 3rd Trial Average Time (s) Average Speed (ft/s)
10 feet
20 feet
30 feet
  1. What’s the difference between speed and velocity?
  2. Calculate the velocities when rolling a ball diagonally across a box that is ten feet long and five feet wide.
    1. Find one of the boxes in the room that is 10 ft long and 5 ft wide.
    2. Draw a diagram on your paper of the box. Include the cardinal directions (North, South, East and West).
    3. When you roll the marble diagonally, you are rolling it in two cardinal directions at once. Which are these (e.g., Northeast, Southwest, etc.)?
    4. Roll the ball along the diagonal at a slow speed. Try and consistently roll at the same speed. Once you have found a good speed, repeat the experiment three times, then take the average of those times.
    5. You can calculate the velocity in each of the above directions by taking the distance along each side and dividing it by the time it took the marble to travel.
Cardinal direction Side of box Length of side Average time Velocity
Long 10 ft            s            ft / s
Short 5 ft            s            ft / s
  1. Which of the two measured velocities was greater: the velocity in the short direction or the velocity in the long direction? Why?
  2. Given your understanding of the difference between speed and velocity, why is the speed of the ball greater than either of the velocities?
Velocity and Acceleration

When calculating velocity, divide distance by time and include the direction that the object is traveling in (v = d/t). For example, going east to Erie, PA which is 100 miles away in 4 hours means that your velocity is 25 miles per hour east.

Acceleration is defined as the change in velocity over time. This means that an object accelerates when its speed changes or its direction changes! An object keeping a constant speed but traveling in a circle is still accelerating due to this change in velocity.

  1. Calculate the velocity (make sure to include direction):
    1. Brittany drives north (direction) 60 miles (distance) in two hours (time).
    2. Brandon walks 100 feet south over the course of five minutes.
    3. David sees a plane travel to the west 1000 meters in one second.
    4. Danielle jumps up to a height of two feet in one second.
    5. Gabrielle drops a ball from the top of the school (20 meters high) and it takes two seconds to fall to the ground.
    6. It takes two seconds for a ball that Jerome throws to reach Steven, standing 50 feet away.

Get a partner, a ball, a stopwatch and calculate the acceleration in the following situations. You do not need to do these in any particular order:

  1. The acceleration from rest of a ball on an inclined plane at a 45-degree angle with the ground. Do the following:
    1. Get an inclined plane and a ball. Place the bottom of the inclined plane at the edge of a floor tile.
    2. Measure and mark the edge of a floor tile 10 feet from the bottom of the inclined plane. You will measure the final velocity of the ball over these 10 feet.
    3. Starting the ball from rest at the top of the inclined plane, measure how long it takes the ball to reach the bottom of the inclined plane three times, then take the average. Measure the length of the inclined plane. Use the average time and the length of the inclined plane to determine the average initial velocity of the ball.
    4. Starting the ball from rest at the top of the inclined plane, measure how long it takes the ball to go from the bottom of the inclined plane to the ten foot mark on the floor. Do this three times, then take the average. Use this average time and the distance (10 feet) to determine the final velocity of the ball.
    5. Using the average time that it took the ball to roll down the inclined plane as the final time and zero as the initial time, calculate the acceleration of the ball.
    6. How does this value compare with acceleration due to gravity, 32 feet per second squared? Why is it different?
  2. The deceleration of a rolled ball over 100 feet. Do the following:
    1. Get another group to work with. You will need a total of four people to do the following tasks: measure the total time & catch the ball, roll the ball & record data, time the initial velocity, and time the final velocity.
    2. In the hallway, measure and mark the edge of floor tiles in the hallway at the following distances: 0 feet, 10 feet, 90 feet and 100 feet.
    3. One person will roll the ball 100 feet down the hallway at least three times, starting at the mark for 0 feet. The person timing the initial velocity will start their stopwatch as soon as the ball crosses the mark for 0 feet and stop when it crosses the mark for 10 feet. The person timing the final velocity will start their stopwatch when it crosses the mark for 90 feet and stop when it crosses the mark for 100 feet. The person catching the ball will start their stopwatch when it crosses the mark for 0 feet and stop when it crosses the mark for 100 feet.
    4. After you have at least three good rolls, calculate the average initial velocity (using 10 feet for the distance), the average final velocity (using 10 feet for the distance), and the average final time (the total time it takes). Use 0 as the initial time and calculate the negative acceleration of the ball over 100 feet.
  3. The final velocity of a dropped ball from 2 meters. Do the following:
    1. Mark a place on a wall that is 2 meters from the floor. Measure how long it takes the ball to fall those two meters by taking an average over three trials.
    2. Because the ball is falling due to gravity, you know that the acceleration is 10 meters per second squared. You have just measured the final time (assuming initial time is 0), and you know that the initial velocity is 0 m/s. Calculate the final velocity.
Newton’s 2nd Law

“F = ma” is “Force is equal to the mass times the acceleration” for any object. Force is measured in Newtons (N). Newtons are kilogram-meters per seconds squared. This means that, in order to calculate the force, you need to have the mass in kg and the acceleration in m/s2. Newton said that the force of an object depends on both its mass and its acceleration. Assume that the acceleration due to gravity is 10 m/s2.

Calculate the force (in N):

F = m * a

  1. A 70-kg (mass) man jumps from an airplane (the acceleration is due to gravity)
  2. A 1000-kg car accelerates at 1 m/s2 (acceleration)
  3. The same 1000-kg car accelerates at 2 m/s2
  4. A 500-kg car accelerates at the same rate (2 m/s2)

Terrace Station

From the front of the room, get a triple-beam balance, one of the objects in the basket and an empty basket. Measure the downward force of the object in front of you in Newtons by following these directions:

  1. Make sure the triple-beam balance starts at 0 grams (on all three beams). Mass the empty basket. What is the mass (in g) of the empty basket?
  2. Put the object in the basket and mass it. What is the mass of the object plus the platform in grams?
  3. Subtract the mass of the platform from the mass of the object and the platform. The result is the mass of the object in grams. What is the mass of the object in g?
  4. To calculate the force of the object due to gravity, we need to get the mass in kg. What is the object’s mass in kg? Given that 1 kg is equal to 1000 g, you know you will need to divide the mass in grams by 1000 in order to find the mass in kg.
  5. Since this object is at rest, we will use gravity (10 m/s2) for the “a” in F = ma. Calculate F (in N).

Return all of the materials back to the front of the room.

Lee Station

Get a basket of three masses from the front of the room. Using Newton’s third law, we know that every action has an equal and opposite reaction.

  1. Using gravity (10 m/s2) for the “a” in F = ma, what is the force of each of these masses on the table?
  2. Since the masses push down on the table, and every action has an equal and opposite reaction, what is the amount of force with which the table is pushing up on each of the masses?
  3. Pick up one of the masses. When you lift the mass up, does it take more, less or the same amount of force than if you hold it steady?
  4. Choose one of the masses. If you accelerate the mass up at 5 m/s2, what is the total force that you must exert on the mass? Since you have to overcome gravity and lift the weight, you need to add those two accelerations together before calculating the force.
  5. If you let the mass fall at an acceleration of 2 m/s2, what is the total force that you are exerting on the mass? Since you are accelerating in the same direction as gravity, you need to subtract the acceleration from gravity before calculating the force.
Momentum Lab

You will complete a lab, calculating lab for six different situations:

  1. 3 different objects moving at (roughly) the same velocity
  2. 1 of these objects moving at three different velocities

You should write hypotheses for the momentum of these various objects.

Include the following:

  1. What is your hypothesis or hypotheses?
  2. What is the independent variable?
  3. What is the dependent variable?
  4. How many times did you repeat the experiment?
  5. Represent the data in appropriate tables, charts and graphs.
  6. Why did you get the results that you did? Explain in terms of concepts that you needed to know in order to do this lab.
  7. Was your hypothesis supported? Why or why not?
  8. How could your hypothesis be modified to find out even more information?

Newton’s 3rd Law
  1. There is a 100 g ball accelerating at 10 m/s2. What is the force exerted by the ground when this ball hits the ground and does not bounce back up?
  2. A woman is pushing against a wall with 50 N of force, and is not moving. What is the force that the wall pushes back on the woman?
  3. The same woman pushes against a different wall with the same amount of force, but breaks through. What do you know about this wall?
  4. A 1 kg ball moves 2 m/s south and hits a 2 kg ball. What is the velocity of the second (2 kg) ball after it has been hit by the first ball?
  5. The same 2 kg ball hits two 1 kg balls at the same time. What is the velocity of each of the 1 kg balls if the 2 kg ball is not moving after the collision and both of the 1 kg balls are moving with the same speed?
  6. The same 2 kg ball hits two 1 kg balls at the same time. However, only one of the 1 kg balls moves, and the 2 kg ball is moving with half the speed of the 1 kg ball.
    1. What is the speed of the 2 kg ball?
    2. What is the speed of the 1 kg ball?
  7. A small, 8,000 kg train crossing an intersection at 100 m/s hits a parked (and thankfully empty) 2,000 kg car head on. What is the new speed of the train now that the car is attached to the front of it?
Friction Lab
  1. What is friction?
  2. Explain (in your own words) the two types of friction: static and rolling.
  3. Perform a lab on the following question: Given two objects, which will have more friction with a surface?  You can measure friction in one of the following ways:
    1. Pull the objects with a spring scale and measure how much force is needed to pull each object
    2. Send the objects down an inclined plane and record how much time it takes the object to get to the bottom
    3. Push the objects with the same force along a flat surface and measure how far the objects go
  4. Write down the three objects that you will use and the surface that you will use. What is your hypothesis?
  5. What is the independent variable?
  6. What is the dependent variable?
  7. Perform the experiment, including repeated trials. How many times did you repeat the experiment?
  8. Represent the data in appropriate tables, charts and graphs.
  9. Which object had the most friction? Which object had the least friction? Why?
  10. Was your hypothesis supported? Why or why not?
  11. How could your hypothesis be modified to find out even more information?
Momentum

From The Physics Classroom

Momentum = m * v

Momentum is a commonly used term in sports. A team that has the momentum is on the move and is going to take some effort to stop. A team that has a lot of momentum is really on the move and is going to be hard to stop. Momentum is a physics term; it refers to the quantity of motion that an object has. A sports team that is on the move has the momentum. If an object is in motion (on the move) then it has momentum.

Momentum can be defined as “mass in motion.” All objects have mass; so if an object is moving, then it has momentum – it has its mass in motion. The amount of momentum that an object has is dependent upon two variables: how much stuff is moving and how fast the stuff is moving. Momentum depends upon the variables mass and velocity. In terms of an equation, the momentum of an object is equal to the mass of the object times the velocity of the object.

  1. Determine the momentum of a:
    1. 60-kg halfback moving eastward at 9 m/s.
    2. 1000-kg car moving northward at 20 m/s.
    3. 40-kg freshman moving southward at 2 m/s.
  2. A car possesses 20,000 units of momentum. What would be the car’s new momentum if:
    1. its velocity was doubled.
    2. its velocity was tripled.
    3. its mass was doubled (by adding more passengers and a greater load)
    4. both its velocity was doubled and its mass was doubled.