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Monday, January 13, 2014

Warm Up For the objects on the left, which of the two has a greater momentum? Which of the two will be harder to stop? Explain or show work for both. . m/2. 3v. Standards : D2a1 Relate, mass, velocity, and linear momentum for a moving object…

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Monday, January 13, 2014

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  1. Warm Up For the objects on the left, which of the two has a greater momentum? Which of the two will be harder to stop? Explain or show work for both. m/2 3v Standards: D2a1 Relate, mass, velocity, and linear momentum for a moving object… Objective: SWBAT demonstrate understanding of momentum for the quiz. v/3 4m Monday, January 13, 2014 Homework M#1 Agenda Warm Up Momentum Quiz Momentum Notes

  2. Warm Up Find the total momentum of this system of objects if, a 2000 kg object has a velocity of 2.2 m/s east, a 1700 kg object has a velocity of 2.4 m/s south. AP PhysicsTuesday 14.01.14Standards: D2b Relate impulse to the change in linear momentum and center-of-mass motion of a system of particlesObjective: SWBAT use knowledge of momentum and impulse solve impulse and stopping distance problems. Agenda • Warm Up • Momentum & Impulse Notes • Momentum & Impulse Practice Homework M#2

  3. Warm Up A car of mass M, traveling at speed V, stops in time T when maximum braking force is applied. Assuming the braking force is independent of mass, what time would be required to stop a car of mass 2M traveling at speed V? a) T/2 b) T c) √(2T) d) 2T e) 4T AP PhysicsWednesday 14.01.15Standards: D2d Calculate the area under a force versus time graph and relate it to the change in momentum of an object. Objective: SWBAT represent Impulse graphically and interpret the physics of the graphs they create. Agenda • Warm Up • Review Homework • Impulse found graphically • Impulse Lab Activity • Begin M#3 Homework Finish M#3

  4. Warm Up Graph the following data and find the Impulse. AP PhysicsThursday 14.01.16Standards: D32&3 Identify when linear momentum is conserved and solve 1 d elastic & inelastic collisions & 2D inelastic collisions. Objective: SWBAT understand when linear momentum is conserved and apply this knowledge to scenarios. Agenda • Warm Up • Review M#3 • Finish Lab • Conservation of Momentum Notes Homework M#4

  5. Warm Up AP PhysicsFriday 14.01.17Standards: D32&3 Identify when linear momentum is conserved and solve 1 d elastic & inelastic collisions & 2D inelastic collisions. Objective: SWBAT SWBAT understand when linear momentum is conserved and apply this knowledge to scenarios. Estimate the impulse measured in the graph below Agenda • Warm Up • Discussion of Lab Results • Conservation of Momentum Notes • Conservation of Momentum Practice F(N) 40 20 2 1 3 t(s) Homework HW due Monday

  6. Guided Practice: Stopping Distance The most powerful tugboats in the world are built in Finland. These boats exert a force with a magnitude of 2.85x106 N. Suppose one of these tugboats is trying to slow a huge barge that has a mass of 2.0x107 kg and is moving with a speed of 3.0 m/s. If the tugboat exerts its maximum force for 21s in the direction opposite to that in which the barge is moving, what will be the change the barge’s momentum? How far will the barge travel before it is brought to a stop?

  7. Momentum Quiz • Is momentum a scalar quantity or a vector quantity? • Give an example where an object’s momentum changes? • What physics concept that we’ve previously learned causes an object’s momentum to change? • The first human-made satellite, Sputnik I, has a mass of 83.6 kg and a momentum with a magnitude of 6.63x105kgm/s. What was the satellite’s speed? • The specially designed armored car that was built for Leonid Brezhnev when he was head of the Soviet Union has a mass of about 6.0x103 kg. Suppose this car is accelerated from rest by a force of 8.0 kN to the east. What is the car’s velocity after 8.0s?

  8. Momentum M#1 • (#1) In 1987, Marisa Canofoglia, of Italy, roller-skated at a record-setting speed of 40.3 km/h. If the magnitude of Canofoglia’smomentumwas 6.60x102kgm/s, what was her mass? • (#3) One of the smallest planes ever flown was the Bumble Bee II, which had a mass of 1.80x102 kg. If the pilot’s mass was 7.0x101 kg, what was the velocity of both plane and pilot if their momentum was 2.08x104kgm/s to the west? • (#4) The firest human-made satellite, Sputnik I, has a mass of 83.6 kg and a momentum with a magnitude of 6.63x105kgm/s. What was the satellite’s speed? • (#6) In 1994, a tower 22.13 m tall was built of Lego blocks. Suppose a block with a mass of 2.00 g is dropped from the top of this tower. Neglecting air resistance, calculate the block’s momentum at the instant the block hits the ground.

  9. Impulse & Stopping Distance M#2 1 (2) A bronze statue of Buddha was completed in Tokyo in 1993. The statue is 35m tall and has a mass of 1.00x106 kg. Suppose this statue were to be moved to a different location . What is the magnitude of the impulse that must act on the statue in order for the speed to increase from 0m/s to 0.20 m/s? If the magnitude of the net force acting on the statue is 12.5 kN, how long will it take for the final speed to be reached? 2. (5) In 1992, Dan Bozich of the United States drove a gasoline-powered gocart at a speed of 125.5 km/h. Suppose Bozich applies the brakes upon reaching this speed. If the combined mass of the go-cart and driver 2.00x102kg, the decelerating force is 3.60x102N opposite the cart’s motion, and the time during which deceleration takes place is 10.0s. What is the final speed of Bozich and the go-cart? 3 (6) The “human cannonball” has long been a popular—and extremely dangerous—circus stunt. in order for a 45 kg person to leave the cannon with the fastest speed yet achieved by a human cannonball, a 1.6x103N force must be exerted on that person for 0.68s. What is the record speed at which a person has been shot from a circus cannon? 4 (2) In 1920, a 6.5x104kg meteorite was found in Africa. Suppose a meteorite with this mass enters Earth’s atmosphere with a speed of 1.0 km/s. What is the change in the meteorite’s momentum if the average constant force of -1.7x106N acts on the meteorite for 30.0s? How far does the meteorite travel during this time. 5. (4) The record for the smallest dog in the world belongs to a terrier who had a mass of only 113 g. Suppose this dog runs to the right with a speed of 2.00 m/s when it suddenly sees a mouse. The dog becomes scared and uses its paws to bring itself to rest in 0.80s. What is the force required to stop the dog? What is the dog’s stopping distance?

  10. Representing Impulse Graphically Taking the area of an F vsΔt graph will enable you to find the Impulse or change of momentum of a system subject to a Force. 2. Find the Impulse of the graph below 1. Find the Impulse of the graph below 20 16 16 12 12 F(N) F(N) 8 8 4 4 0.5 1.0 1.5 0.5 1.0 1.5 2.0 2.5 Δt(s) Δt(s)

  11. Lab Activity – Sketching F vsΔt graphs for various objects Demo: Car pulling kart by string: Observe the Impulse on the spring scale. Activity: For a 500 g mass you will hook up a spring scale to a motorized car, and you will drag the object for 1 meter. Complete at least 5 trials for and average them for accuracy. Record the total distance traveled, the total time traveled. Record the time the scale reaches maximum Force and the time it drops to a steady state (constant) force.

  12. Impulse Graph Questions M#3 • Create a F vsΔt graph • Estimate the total Impulse required to speed up the object to its constant speed. • What is the total Impulse required to maintain the constant speed of the object? • Is the momentum actually changing when the object is moving at a constant speed? If no, explain why our impulse is not 0? • Calculate the average speed using distance/time, then using Impulse. Compare your answers. Explain the similarities or differences?

  13. Conservation of Momentum 1. Kangaroos are good runners that can sustain a speed of 56 km/h (15.5 m/s). Suppose a kangaroo is sitting on a log that is floating in a lake. When the kangaroo gets scared, she jumps off the log with a velocity of 15 m/s toward the bank. The log moves with a velocity of 3.8 m/s away from the bank. If the mass of the log is 250 kg, what is the mass of the kangaroo?

  14. Conservation of Momentum Practice M#4 • The largest grand piano in the world is really grand. Built in London, it has a mass of 1.25x103kg. Suppose a pianist finishes playing this piano and pushes herself from the piano so that she rolls backwards with a speed of 1.4 m/s. Meanwhile, the piano rolls forward so that in 4.0 s it travels 24 cm at constant velocity. Assuming the stool that the pianist is sitting on has a negligible mass, what is the pianist’s mass? • With a mass of 114 kg, Baby Bird is the smallest monoplane ever flown. Suppose the Baby Bird and pilot are coasting along the runway when the pilot jumps horizontally to the runway behind the plane. The pilot’s velocity upon leaving he plane is 5.32 m/s backward. After the pilot jumps from the plane, the plane coasts forward with a speed of 3.40 m/s. If the pilot’s mass equals 60.0 kg, what is the velocity of the plane and pilot before the pilot jumps. • The largest frog ever found was discovered in Cameroon in 1989. The frog’s mass was nearly 3.6 kg. Suppose this frog is placed on a skateboard with a mass of 3.0 kg. The frog jumps horizontally off the skateboard to the right, and the skateboard rolls freely in the opposite direction with a speed of 2.0 m/s relative to the ground. If the frog and skateboard are initially at rest, what is the initial horizontal velocity of the frog? • In 1994, ,a pumpkin with a mass of 449 kg was grown in Canada. Suppose you want to push a pumpkin with this mass along a smooth, horizontal ramp. You give the pumpkin a good push, only to find yourself sliding backwards at a speed of 4.0 m/s. How far will the pumpkin slide 3.0 s after the push? Assume your mass to be 60.0 kg.

  15. ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` Perfectly inelastic collisions vb vr Elastic is like a rubber band. It stretches, it pushes back on you or bounces back, like a spring. So an inelastic collision is a collision where there is no bounce. In this case, there is a crunch. -Momentum is conserved during inelastic collisions, even though mechanical energy is not conserved in this situation. Why do you think mechanical energy is not conserved in inelastic collisions? Where does the energy go? vbr Before After

  16. ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` Elastic Collisions vb vr vb vr In elastic collisions the two objects bounce off each other with no mechanical energy lost to heat, sound, or deformation of the object. When no external force is present momentum is conserved so: mrvri+mbvbi=mrvrf+mvbf After Before

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