Tossing a Brick

SCIENCE CONCEPT:

The relationship between force and motion is the subject of a branch of the science of physics known as mechanics and it is one of the oldest of the sciences. You know that it takes more force to throw an iron ball than a tennis ball. An iron ball is heavier than a tennis ball, but it is not the weight that makes it harder to throw. If there were no gravity, so that the balls had no weight, the iron ball would still be harder to throw. The iron ball has a greater amount of matter or material in it and matter resists being accelerated. Newton called the measure of the amount of material in an object its mass.

STUDENT OBJECTIVE:

The student will explore acceleration in relationship to force and mass while throwing a brick. The student will throw the brick different distances to compare the force and mass in relationship to the acceleration needed to toss the brick.

OVERVIEW:

Students in this activity, will divide into teams of 3 and take turns tossing the brick different distances. Safety and measurement will be apart of the lesson.

PREPARATION TIME:

Variable

LESSON TIME:

30 minutes.

TEACHER PREP:

Gather materials

WORDS TO KNOW:

acceleration

force

weight

mass

quantities

TEACHER TEXT:

Mass is the resistance to being accelerated and weight is the force of the earth's gravity pulling on an object. These are often confused even by scientists and engineers. An object has the same mass everywhere in the universe. It has weight only where there is gravity.

On earth mass and weight are directly related and so they are often mixed up. Objects with a greater mass have a greater weight in direction proportion. An object with twice the mass weights twice as much. Because mass and weight are so directly connected, we often interchange one for the other without being aware of the difference. In the United States, where the English system is widely used, the scales will measure the force of gravity on your body (your weight) in pounds. Mass is rarely used.

Newton's Second Law of Motion says that force is equal to mass times acceleration: Force = Mass x Acceleration. This tells how much force there is when a certain amount of mass is accelerated. We can also turn this formula around to find the amount of acceleration that a force will give to a certain mass.

acceleration =	Force
	Mass

A mathematical formula such as this is valuable because it tells the exact relationship between the different quantities. If you double the amount of mass, for example, then it will take twice the force to give it the same acceleration. Also, if any two of the quantities in the formula are known, the other can be figured out.

If the force and acceleration are known, the mass can be calculated. This is how the mass of objects like the earth, moon, and sun have been found. Imagine trying to 'weigh' the earth (actually to find its mass) any other way.

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Last modified: Tue Mar 24 16:31:49 PST 1998