Monday, October 28, 2013

H PhysicsStandards: 1c Students know how to apply F=ma to solve one-dimensional motion problems that involve constant forces.

Learning Objective: SWBAT design an experiment to test Newton’s 2nd Law

Agenda: 1. Warm Up2. Review HW3. Newton’s 2nd Law Lab

HomeworkBegin working on HW Problems Worksheet #F2: Due Wednesday

Warm UpWhat is the net force on

the box?

8N3N

1N

4N

Tuesday, October 29, 2013

H Physics

Warm UpIf the cart from yesterday’s lab is pushed down by 3 N of force and it has a mass of .15 kg, how fast would it

accelerate?

HomeworkWorksheet #F2: Due Thursday

Standards: 1c Students know how to apply F=ma to solve one-dimensional motion problems that involve constant forces.

Learning Objective: SWBAT design an experiment to test Newton’s 2nd Law

Agenda: 1. Warm Up2. Review Lab Day 13. Newton’s 2nd Law Lab

Continued

Wednesday, October 30, 2013

H PhysicsWarm Up

If you want to prove that an object is accelerating, what data will you collect? What shape will your graph be?

HomeworkBegin working on HW Problems Worksheet #F2: Due Friday

Standards: Standards: 1c Students know how to apply F=ma to solve one-dimensional motion problems that involve constant forces.

Learning Objective: SWBAT take 2 sets of data to show how acceleration is affected by changing mass.

Agenda: 1. Warm Up2. Turn in Part 1 of lab3. Write a hypothesis for question 2

and 34. Collect Data For Part 2 & 3

Thursday, November 1, 2013

H Physics

HomeworkNewton’s 2nd Law #F2

Warm UpWhat is the weight in N, of a

25g object?

Standards: 1c Students know how to apply F=ma to solve one-dimensional motion problems that involve constant forces.

Learning Objective: SWBAT solve Newton’s 2nd Law problems

Agenda1. Review Lab2. Force Notes3. Force Practice Problems

Friday , November 2, 2013

H Physics

Homework#F2 & #FH3 due Monday

Warm UpIf an object’s mass is 20

kg, and it is being pushed with a Force of 100N, what

will be the object’s acceleration?

Standards: 1c Students know how to apply F=ma to solve one-dimensional motion problems that involve constant forces.

Learning Objective: SWBAT reflect and discuss lab results and apply what they’ve learned to answer questions.

Agenda: 1. Warm Up2. Lab Report Review3. Turn in Part 2 & 3 of

Lab

Symbols, units and equations Study Guide

--distance(d) anddisplacement (Δx or Δy ) units: meters (m)--speed (vs),velocity (v) units: meters per second or kilometers per hour (m/s, or km/hr)--acceleration (a) units: meters per second squared or kilometers per hour squared (m/s2, km/hr2) --time or change in time (t or Δt) units: seconds

Equations:

Constant Velocity

Constant Acceleration

1.

2.

The Two equations of Motion The Two equations of Motion for Falling Objects ag=-9.8m/s2

Forces

Profile of A Force• Force is a vector (direction matters!)• The Units of Force are Newtons (N) or it can

also be written as kilograms times meters per second squared (kg*m/s2)

• Equation: Fnet=MA o Fnet is the result of adding allo of the forces together.

Types of Forces• From your book p. 94 Table 4-2

Force Symbol Definition Direction

Friction Ff Resistive Force. Comes from rubbing against or sliding across surfaces.

Parallel to the surface and opposite the direction of sliding

Normal FN The force exerted on an object by the ground, a table, a platform, or any surface.

Perpendicular to and away from the surface.

Spring Fsp Restoring Force. The push or pull a spring exerts on an object.

Opposite the displacements of the object at the end of the spring.

Tension FT The pull exerted by a string, rope, or cable when attached to something.

Away from the object and parallel to the string, rope, or cable at the pont of attachment.

Thrust Fthrust,Fap A general term for the forces that move objects such as rockets, planes, cars and people.

In the same direction as the acceleration of the object.

Weight Fg Attractive Force of two objects due to gravity. Usually Earth and and object

Straight down towards the center of the earth.

Air Resistance/Drag FAR Resistive Force, comes from air/wind hitting moving objects

Opposite of Motion

Calculating Net Force1. 5 N West, 3 N West Fnet=?2. 15 N West, 10 N East, 7 N West Fnet=?3. 2 N West, 1 N East, 7 N West, 8 N East Fnet=?4. 4 N North, 4 N South, Fnet=?5. 6 N North, 2 N West, 4N East, 7 N South Fnet=?

#F1a

Force each of the following draw a diagram for each and solve.

#F1b

Carts & MassesEngage - You will construct gliders to be launched from a catapult at the end of the unit but not yet–at this point in time, Today, you are going to design an experiment to determine what happens to an object when there’s a net force acting on it. Explore - Students are shown the experimental setup (Figure 4).Respond following questions, and provide an explanation for your thoughts:

o What will happen to the cart when there is a force applied to it? o What if the applied force is increased? What about the cart’s motion will

change?o What if the cart’s own mass is increased? How will its motion change?

Test - Design and execute experiments to test your hypothesis from the explore section (at least 5 trials for each hypothesis). Explain – Make a graph for each set of data. You decide what you think you should graph. ElaborateClass Discussion QuestionsWhy is it a good idea to do multiple trials?

o “What aspects” changed from one trial to the next?o What variable did you change on purpose?o What variable changed as an effect of changing your independent

variable?Newton’s 2nd Law Questions:

o What happens if we apply a net force on an object?o What happens if that net force is increased?o What happens if the mass of the object itself increases?

We have a mathematical expression for this: Fnet = ma.EvaluateComplete HW #F2

Figure 4. Experimental setup for cart & mass activity

Cart and Masses Lab Instructions

• Part 1 Due Todayo Use Δx=(1/2)at2 to find the average accelerationo Use your x vs t graph to prove the object is accelerating

• Part 2 Due Thursday• All data must be collected IN CLASS• Use Fnet=ma to find the acceleration. Compare this to the average

acceleration you can calculate from Δx=(1/2)at2. Explain the differences

• Graph Fnet vs m and use this graph to prove your hypothesis• Part 3 Due Thursday

• All data must be collected IN CLASS• Use Fnet=ma to find the acceleration. Compare this to the average

acceleration you can calculate from Δx=(1/2)at2. Explain the differences.

• Graph Fnet vs m and use this graph to prove your hypothesis.

EVERY PERSON WILL TURN IN THE FOLLOWING

Newton’s 2nd Law Problems

 1. If a student accelerates on his/her bicycle at 4m/s2, and the student has a mass of 77 kg. How much force does s/he apply to the bicycle?2. Find the weight of the following people: Rickey is 100 kg, Manny is 150kg, and Donna is 65kg and the acceleration due to gravity is 9.8m/s2. 3 How much force does a baseball experience if the baseball bat accelerates the ball at 8m/s2 and the mass of the baseball is 5kg? 4. How much force would a 10kg baseball experience if the bat accelerated the ball at 20m/s2?5. What is the mass of a bullet that accelerates at 100m/s2 by a 12 N Force when shot out of a gun?6a. Thrust from a rocket’s engine equal to 100,000 N launches a shuttle with a mass of 10,000 kg into the air. What is the rockets acceleration? 6b*If the acceleration due to gravity is 9.8 m/s2 will the rocket be able to escape the earths atmosphere?7. A wide receiver (90 kg) is tackled after catching a football by one of the safeties (99 kg). The safety applies a force of 250N? How fast did the receiver decelerate? (Be careful when you choose which mass to use.)

#F2

Newton’s 2nd Law 2 #FH3

1. What does Fnet mean?2. What is the equation Newton’s 2nd Law.3. What do you change from Newton’s 2nd Law equation in order to find

weight (W or Fg) ? 4. Find the net force of mini car racing if friction is 20N, the accelerator

supplies 50N, and air resistance is slowing it down by 2N.5. If the car from problem 4 has a mass of 1 kg, what is the car’s

acceleration? 6. Which direction does Gravitational Force push?7. Describe the Normal Force? 8. Friction acts in which direction? 9. If an object is flying northeast, which direction is air resistance pushing?10. Find the mass of an object if it accelerates at 2 m/s2, when 20N of Force

pushes it. 11. Find the mass of an object if it accelerates at 2 m/s2, when there is an

applied force of 80 N, a force of friction of 20N, and air resistance of 10N.

12. Find the applied Force if a 20kg object is accelerated at 10m/s2 and friction is opposing the motion with 30N of Force.