Students: You will be doing two experiments (or more if you want) using the scientific method and reporting results in your journals. Feel free to draw pictures.
The first experiment is to select one of Newton’s laws below and the second is a real life example using the scientific method to find a solution to anything around you. Example: What is the best way to treat your pets so they trust you? Or: Germs can be sticky. How can I find out how long it takes to get germs off my hands when I wash?
Get your parents to help you!
Note before you perform the experiments, write your predictions first, how you will do the experiment, do the experiment, record your results and your explanation using the correct law. Do not read the answers until after you have your results recorded.
Inertia: Newton’s First Law of Motion
Newton’s First Law of Motion, also known as the Law of Inertia, states that an object’s velocity or speed will not change unless it is acted on by an outside force. This means that an object at rest will stay at rest until a force causes it to move. Likewise, an object in motion will stay in motion until a force acts on it and causes its velocity to change. On earth there is gravity and air resistance to slow objects down.
You can do a simple inertia experiment to demonstrate this. Have your parents help you or you’ll have egg on your face! J You’ll need a hard-boiled egg and a raw egg for this activity. You will be spinning both eggs following the below instructions. What is your prediction for this experiment for how the eggs will behave based on the first law? Write it down first then write down what you will do to test your prediction. Write the results and explanation.
Procedure: First, spin the hard-boiled egg on its side. When it’s going fast, gently put your fingers down on it to stop it and then move your hand off immediately when it stops. Next, spin the raw egg. Stop it in the same way you did with the hard-boiled egg you let go.
ANSWER STOP! (Do your experiment and explanation first!):
What happens? The egg should start to turn again. After The motion of the liquid within the egg is still going; the force you exerted was not enough to stop both the inertia of the shell and the inertia of the liquid inside of it. If you held the egg longer, enough force would have been exerted to stop the egg completely.
The results of the experiment fit in with the Law of Inertia: an object will continue to remain in one state until sufficient outside force acts upon it, either to put it in motion or to bring it to rest.
The greater mass or velocity an object has, the greater its inertia.
Perform a real life experiment at the grocery store. It takes a strong push to get a loaded shopping cart moving, but once it gathers speed it keeps going even if you let go of the handle. When you stop a moving cart full of groceries, it takes much more force to stop it than an empty cart (one with less mass). Likewise, it takes more force to brake a fast-moving bike than a slow one (one with less velocity), even though the mass of each is equal.
For further thought: Why do wheels and tops eventually stop spinning, without appearing to be touched by a force?
Newton‘s Second Law of Motion
Newton’s Second Law of Motion states that “when an object is acted on by an outside force, the strength of the force equals the mass of the object times the resulting acceleration”. In other words, the formula to use in calculating force is force=mass times acceleration. Opposing forces such as friction can be added or subtracted from the total to find the amount of force that was really used in a situation.
You can demonstrate this principle by dropping a rock or marble and a wadded-up piece of paper at the same time. Write down your prediction first of what will happen and how you will demonstrate the second law of motion. If you drop the two objects into a dish of sand or flour, you can see how different the force of impact for each object was, based on the crater made in the sand by each one. Measure the depth of the crater hole. Write your results and explanation.
They fall at an equal rate and their acceleration is constant due to the force of gravity acting on them. However, the rock has a much greater force of impact when it hits the ground, because of its greater mass. Another way to show this is two push off two toy cars or roller skates of equal mass at the same time, giving one of them a harder push than the other. The mass is equal in both, but the acceleration is greater in the one that you exerted greater force on.
What other tests can you do?
Newton‘s Third Law of Motion
Stated simply, Newton’s Third Law of Motion says that “for every action, there is an equal and opposite reaction.”
If you have a skate board or wagon, sit down on the board or wagon and throw a heavy ball. You can also demonstrate this by walking. Note when you walk that you are pushing backward with your feet. Now try to walk forward pushing forward with your feet. Write down your predictions before testing and how you will do the test. Write your results and explanation.
The force of throwing the ball pushes your skates (and you) in the other direction. Pushing the wrong direction with your foot breaks the third law and you rock back and forth instead of moving forward.
For further thought: Thrust is an important result of Newton’s Third Law. How does this work in a rocket?