Forces

Forces

Some physics fun with Newton’s Laws of Motion.

Introduction

What happens when a bat hits a baseball? Why does a rolling ball eventually stop? How do we walk, jump or run? The answer lies in physics! In this topic, students get the chance to explore how Newton’s Laws of Motion explain the way that things move.

You won’t have to force your students to learn — they’ll push, pull, drop, roll, and fling their way through a variety of demonstrations and activities illustrating the forces on everything around us.

Objectives     

• Generally describe what a force is, and name some common forces.
• Describe gravitational force, and how this force pulls objects towards the Earth at the same rate, regardless of mass.
• Describe a scenario that demonstrates the property of inertia.
• Understand the concept of action and reaction forces.
• Compare the effect of friction on the movement of an object over a variety of surfaces.

Background

The basis of classical mechanics (the study of ‘how stuff moves’), Newton’s Three Laws of Motion, can be used to explain the movements of everything from prodigious planets to petite platelets.

First Law: The Law of Inertia
Every object persists in its state of rest or uniform motion¬ in a straight line unless it is compelled to change that state by external forces.
Without a force (a push or a pull) intervening, objects tend to keep moving if they’re moving and tend to stay stopped if they’re stopped. Examples of this are astronauts in space, who keep on moving in a straight line until they bump into something, or a ball that won’t move on its own until you kick or push it.

Second Law: Force = mass x acceleration
Force is equal to the change in momentum per change in time. For a constant mass, force equals mass times acceleration.
Things with more mass (heavier things) require more force to speed up as quickly as things with less mass (lighter things). Imagine trying to throw an orange and a watermelon. The bigger the force, the greater the acceleration (the change in an object’s velocity). It’s also harder to stop a heavier object than it is to stop a lighter one.

Third Law: For every action there is an equal and opposite reaction.
If you push on something, it will push back. For example, your feet have to push back on the ground in order for you to walk forward. The explosive combustion inside a rocket throws exhaust out its bottom, and propels the rocket upwards with equal force.

Entire Lesson

These resources are free!
You must LOGIN to download the full lesson + activities.   

Other Resources

Science World at TELUS World of Science | Mitchell Odyssey Foundation Gallery: Eureka!
Science World | Online Games | Eureka! Games
Science Monster | Gravity and Inertia
Newton’s Three Laws of Motion