January+Physics+Lab

Physical Science- Transfer of Motion- Background Information for the Lab



Everything in the universe is in motion. Motion occurs when an object changes its position in space. Objects move in straight lines or curved lines.

This English physicist and mathematician formulated fundamental laws of gravity and motion. He also discovered that light is made up of a spectrum of colors, and he built the first reflecting telescope.
 * __Sir Isaac Newton (1642-1727)__**

If an object is not being acted upon by a force, it will stay still or continue moving at a constant speed in a straight line.
 * __Newton’s First Law of Motion__**

Any resultant force acting on an object will change its motion. How much the motion changes depends on the object’s mass and the size of the resultant force.
 * __Newton__****__’s Second Las of Motion__**

When an object A exerts a force on an object B, then B exerts an equal an opposite force on A.
 * __Newton__****__’s Third Law of Motion__**
 * __Force-__** A force is either a push or a pull. The motion of objects can be changed by forces. The size of the change is related to the size of the force. The change is also related to the weight (mass) of the object on which the force is being exerted. When an object does not move in response to a force, it is because another force is being applied by the environment. Forces can make things move faster or slower, stop, change direction, or change size or shape.

Forces affect objects in many different ways. There are forces you can see, such as a foot kicking a ball, and invisible forces, such as magnetism and gravity. The magnetic force which pulls tacks onto a magnet is an invisible force. You can see the pulling forces at work in a tug of war. The team that pulls with the most force wins.
 * __Types of forces__**

A single force acting on an object will make it start to move, or move faster or slower. Two equal forces acting in opposite directions try to change the object’s size or shape. Forces need 2 or more objects to be touching each other are called **__contact forces__**. You are sing contact forces when you move an object with your hands. When you kick a ball, the single force of your kick pushes the ball to start to move. As you catch the ball, the pushing force of your hands makes the ball slow down and stop. As you step on a ball, the equal forces of your foot pushing down and the ground pushing up work to make the ball stop.

When you roll one ball into another on a smooth surface, the force of your movement will set the ball moving. The moving ball will exert force on the stationary one, causing it to move too. The surface will exert a force (friction) on both balls causing them to both slow down, and eventually stop.

Speed is the rate of motion, which measures how far an object travels in a certain length of time.
 * __Speed__**

Velocity describes an object’s speed and direction. Acceleration occurs when an object’s velocity changes over a period of time.
 * __Velocity__**
 * __Acceleration__**

Friction is the resistance to motion.
 * __Friction__**

Six tables each with the following:
 * __Material for Lab:__**

2 cars with a spring attached to the front 2 cars with Velcro attached to the front 1 meter stick Taped line from which to start cars Optional- (weight for each car) Lab Procedure: Engaging scenario: When two football players of about the same weight run into each other, what happens? If they are of very different weights what happens to the lighter player? What happens to the heavier player?

Or visualize this: Begin with a rollerblade demonstration. Tell the students they will think about what will happen. Students of the same weight wear rollerblades.
 * 1) One person stands still. The other person skates into him. At the point when they would collide, they push off each other.
 * 2) Repeat above but this time, as they meet they grab onto each other.
 * 3) Both students skate towards each other. When they meet, they push off from each other.
 * 4) Repeat above, but this time they grab onto each other.

This entire process can be repeated using one heavier students ( or 2 students together) and one lighter student. See if the results are the same. Now try the same process using 2 cars at a table.
 * 1) One car moving- one car still. The springs on the cars are facing each other. Observation: The moving car stops and the still car moves in the same direction the moving car was going.
 * 2) One car moving- one car still. The Velcro on the cars is facing each other. Observation: the cars stick together and move slowly in the direction the moving car was going.
 * 3) Both cars moving towards each other. The springs on the cars are facing each other. Observation: Each cars moves in the opposite direction but slower.
 * 4) Both cars moving towards each other. The Velcro on the cars facing each other. Observation: The cars stop.

These demonstrations can be repeated putting a weight on one of the cars. Some of the observations will differ. Students should observe that movement transfers fro one car to the other. This is called transfer of momentum. They should also see that the weight of the other car (or other object) affects the speed and direction of the movement.

Assessment: Students should be able to describe what “transfer” means, when discussing transfer of momentum.