Warm Up A 200 kg piano falls from the sky. How much does the piano weigh? Monday, November 4, 2013 Physics Standards: 1c Students know how to apply F=ma to solve one-dimensional motion problems that involve constant forces. Learning Objective: SWBAT create a force meter to study gravity Agenda: Warm Up Force Meter Lab Gravity Discussion Put a scale on the force meter. Homework #FH4
Warm Up Find the net force of a 1kg ball accelerating under a 55N Force, when friction is 16N and air resistance is 8N? Tuesday, November 5, 2013 Physics Standards: 1c Students know how to apply F=ma to solve one-dimensional motion problems that involve constant forces. Learning Objective: SWBAT build a force meter and use it to understand how gravity works. Agenda: Warm Up Review Test Take Survey Finish Lab Homework #F4
Wednesday, November 6, 2013Physics Standards: Standards: 1c Students know how to apply F=ma to solve one-dimensional motion problems that involve constant forces. Learning Objective: SWBAT understand how weight functions and build a a Force meter. Agenda: Warm Up Discuss Mousetrap Car Lab Tell Students their grades Finish Force Meter Lab Homework #F4 Warm Up If a 1000kg car accelerates at 5 m/s2, what is the applied Force of the car’s engine.
Thursday, November 7, 2013 Physics Standards: Standards: Standards: 1c Students know how to apply F=ma to solve one-dimensional motion problems that involve constant forces. Learning Objective: SWBAT : SWBAT understand how weight functions and build a a Force meter. Homework NA Agenda Warm Up Review Homework Finish Force Meter Warm Up How much does 200g weigh?
Warm Up If your Force Meter reads 9N when an object of unknown mass hangs from it, find the mass. Friday, November 8, 2013 Physics • Standards: 1c Students know how to apply F=ma to solve one-dimensional motion problems that involve constant forces. • Learning Objective: SWBAT • Agenda: • Warm Up • Newton’s 3rd Law Tug of War Lab • Engage – Predict result of pushing roller chairs • Explore- Predict Force Meter Readings • Explain – N’s 3rd Law Mini Lecture • Elaborate – Take Measurements with Masses on the end of the force meters. • Discuss Results • Evaluate#F5 Newton’s 3rd Law Homework #F5 Newton’s 3rd Law
Symbols, units and equations Study Guide --distance(d) and displacement (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 Forces The Two equations of Motion The Two equations of Motion for Falling Objects 1. ag=-9.8m/s2 2.
Force Meters • Force Meters • Objective: Students construct rubber band force-meters to aid in the investigation of forces and Newton’s 3rd Law. See Figure 5. • Engage • Watch Video: • Why do objects weigh less on the moon? • What else might affect the weight of an object?” • Explore • How can we use a rubber band to actually determine the weight (the force due to gravity) of an object? • Explain • In order to actually put numbers on our force meters, we have to know the formula for figuring put the amount of gravitational force Fg from a certain amount of mass m. • The formula is Fg= mg (or W = mg) • Elaborate • How is this related to Newton’s 2nd Law, Fnet= ma?” • Evaluate • Students should now create an accurately labeled scale on their force-meters, displaying the applied force in units of Newtons. • Problem Set: #F4 Fg = mg. Figure 5. Rubber band force-meter
Types of Forces • From your book p. 94 Table 4-2
Newton’s 2nd Law Problems #F2 • 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/s2and 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/s2by 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.)
Newton’s 2nd Law 2 #F3 • What does Fnetmean? • What is the equation Newton’s 2nd Law. • What do you change from Newton’s 2nd Law equation in order to find weight (W or Fg) ? • 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. • If the car from problem 4 has a mass of 1 kg, what is the car’s acceleration? • Which direction does Gravitational Force push? • Describe the Normal Force? • Friction acts in which direction? • If an object is flying northeast, which direction is air resistance pushing? • Find the mass of an object if it accelerates at 2 m/s2, when 20N of Force pushes it.
Weight: Problem Set #F4 • What is the weight of a 60kg person? • What is the weight of the 10kg object? • A 4kg and a 6kg object fall from a plane. How much more Force will the 6kg object hit the ground with than the 4kg object? • The 4kg and 6kg object both fall from a plane 10,000 m above the ground. Which one will hit first? • Find the weight of a 300g object (in Newtons)? • An object weighs 10,000N on an unknown celestial body, but only has a mass of 0.5 kg. What must be the acceleration of gravity on this celestial body? • Find the acceleration due to gravity on the moon if gravity on the moon is 1/6 of earths 9.8 m/s2? • Use your answer from the previous problem to find the weight of a 90 kg object on the moon. • Find the mass of a plane whose weight is 4x105N? • If it takes 2s for a 10kg object to fall 100 m from rest on an unknown planet, what is the planet’s acceleration of gravity?
Student Learning Survey • Before taking the test, how confident did you feel about your understanding of Kinematics (motion)? • After taking the test, how confident did you feel? • Do you still try to succeed in this class? If not, what made you stop trying? • I learned Physics the best when Mr. Ancalade did……. • Do you do homework? If you do, does it help? If you don’t, why don’t you do homework? • If you did not turn in the cart and mass lab, why didn’t you? If you did not complete any portion of the lab, what was the reason? • I spend _____ minutes on Physics homework per night. • I spend ______ minutes studying for tests. • I spend ______ minutes studying for quizzes. • Is it helpful when Mr. Ancalade does problems on the board? If yes, explain how it helps. If no or not really, what are the reasons it doesn’t help or only helps a little? • When I don’t understand how to do something in the class, what do I do? If you don’t ask your peers or myself, what are your reasons?
N’s 3rd Law: Tug-of-War To get a Full 10 pts. complete every section with questions. That does not include the explain section (which is lecture) or the Evaluate Section (I will grade this section separately) Write on a separate sheet. • Figures 6 (a) and (b): A student and a partner each pull on the opposing force-meters and observe that they show the same reading. In the second scenario, one student holds his force-meter still, while the partner pulls his force meter to the right. • Figures 7 (a) and (b): Students predict the reading on the force meter in each of the two scenarios depicted prior to testing. • Engage • What will happen to the motion of each chair when one of the students on the rolling chair pushes the other student on the rolling chair. Will it matter which student pushes? Justify your answer. Tell me your reasoning. • Explore • Students attach their force-meters with rubber bands or string and record… • the reading on each force-meter when both students pull (Figure 6 a.) • the reading on each force-meter when one student keeps his force-meter stationary while the other student pulls (Figure 6 b.) • Explain • Newton’s 3rdLaw mini-lecture • Elaborate • Recreate the Figures 7(a) and (b). Write predictions for the force-meter readings for each of the two scenarios in Figure 7 . • Next, test your predictions, discuss your results in a group and be ready to participate in a discussion about these results. • Evaluate • Newton’s 3rd Law Assignment: #F5 Due Monday
Newton’s 3rd Law Notes 1. Using your Engage Experience, define Newton’s 3rd Law - 3 minutes. 2. Discussion - 2 minutes A B FBA= -FAB FBA FAB Notes 5 mins