Name: Curt Wyman

Title of lesson: F = ma, Newton’s Second Law

Date of lesson: Fall, 2005 Second Six Weeks

Length of lesson: 75 Mins

Description of the class:

Grade level: High School Physics

Sources for the lesson:

Holt Physics textbook, chap 4

AISG Physics IPG’s

Texas Essential Knowledge and Skills for Science

Consultations with M. Marder and K. Oehler

TEKS addressed:

4. The student knows the laws governing motion.

The student is expected to be able to:

(A) generate and interpret graphs describing motion including the use of real-time technology;

(B) analyze examples of uniform and accelerated motion including linear, projectile, and circular;

(C) demonstrate the effects of forces on the motion of objects;

The Lesson: F = ma, Newton’s Second Law

I. Overview

In this lesson, students will perform a simple experiment to demonstrate the affect a constant force has on the acceleration of objects of different masses.

II. Performance or learner outcomes

The students will be able to:

1. Demonstrate the effects of Force on the acceleration of an object.

2. Explain the relationship between Force, mass and acceleration.

III. Resources, materials and supplies needed

1. Weights

2. Pulleys and cords

3. Small cart

4. Timer

5. Meter stick

6. Lesson handout and data chart (attached)

Five E Organization

Teacher Does Student Does

Engage: Time: 9:00 AM – 9:10 AM Today we will study Newton’s 2^nd Law. What are the units for force or weight? It’s interesting that the units for force have the same name isn’t it. Demonstration: Ask for two volunteers. Have one student sit in a wheeled chair and the other student push the first student until they start rolling. What happened? What was their initial velocity? Did they achieve some velocity? What does that mean when the velocity increases? What caused the aceleration? What’s a more technical term for “push?” Right, so the force applied to the mass created an acceleration.

Newtons. Volunteers perform the task. Other students watch. The student in the chair began rolling. The initial velocity was zero. Yes. They accelerated. The first person pushing. Applying a force.

Explore: Time 9:10 AM – 9:30 AM Ask the students pick up their lab directions and to go to their designated lab tables with their lab teams. Tell the students that they have 20 minutes to set up the apparatus and take their data. Observe the various groups and see that they are staying on task and are able to make the experiment work. Time: 9:28 AM – 9:30 AM “Two minutes left. You should have all of your data now and be performing the analysis. How many are still taking data?” Time: 9:30 – 9:50AM Ask the students to proceed with part 2 of the lab instructions. Time: 9:50 – 10:00AM Ask the students to take down their equipment and return it to the equipment area and return to their desks.

Student move into their groups and sit at their lab table. The “Materials Person” gets the equipment while the other students read the instructions. The students set up the equipment and record data per the attached lab instructions. Continuing to work either at taking data or at analyzing their data. Perform the calculations for velocity and acceleration and plot a graph of mass vs acceleration. The students take their equipment back to the equipment area and return to their desks.

Explain: Time: 10:00 AM – 10:15 AM If you apply a constant force on an object, what will happen to it? What does that mean, to speed up? If you apply the same constant force to two objects of different mass, what happens? How much more quickly?

It will speed up, accelerate. The speed increases. The smaller mass will accelerate more quickly. A = F/m

Extend/Elaborate: If you’re in a car stopped and you stomp on the accelerator, what do you feel? How fast do you have to go to feel that? What do you feel when you’re driving straight down the highway at 70mph? What about if you were going 100mph? So when a roller coaster ride is exciting, what’s happening? What’s Newton’s 2^nd Law? And what are the units for force?

You feel yourself being pushed back in the seat. 30 mph. 50 mph is more noticeable. Nothing much. You still wouldn’t feel anything. You are accelerating. F = ma Newtons.

Name: ________________ date: _____________

Lab Role: _____________ Group #: _________

LAB TITILE: F=ma, Newton’s Second Law

PURPOSE: To learn about the relationship involving Force, mass and acceleration.

MATERIALS: Weights, string, cart, pulley, timer

INTRODUCTION: This activity demonstrates the affects of different masses on acceleration in the presence of a constant force.

DIRECTIONS: Set up the apparatus as shown.

The weight under the table will apply a constant force on the cart.

Mark the start and stop points for the cart two meters apart. Pull the cart to the start

point, put on the appropriate mass, and release the cart as you start the timer for each run.

PART 1, Qualitative analysis: What will happen when you increase the mass?

Record the mass and time for three different masses. Average three times for each mass.

What happens when the mass is increased?

PART 2, Quantitative Analysis: Calculate the acceleration.

Calculate the average velocity of the cart for each mass. (d = v t)

What is the initial velocity?

What is the final velocity?

Calculate the acceleration. (a = vt)

The total mass of the system is the mass of the cart plus the mass that you added, plus the mass on the weight under the table. Add up the total mass and plot the total mass vs. the acceleration.

What is the relationship between the mass and the acceleration?

What is the shape of your graph?

What would a second curve look like if you increased the constant force and re-took all

of your data?

What would the acceleration be for a very large mass?

What is the formula?

	Physics Lab - F=ma
Trial	Mass	time	avg Velocity	final Velocity	Acceleration	Distance	Force	Tot. Mass
	Kg	sec	m/sec	m/sec	m/sec2	m	N	kg
1
2
3
avg
1
2
3
avg
1
2
3
avg