Torque, Momentum, Impulse,, Energy 2-9 is Torque 10-16 is momentum.

Torque, Momentum, Impulse,, Energy 2-9 is Torque 10-16 is momentum

Weight vs. Mass Weight is mass times gravity W= mg or F w =mg Mass in kilograms Gravity is 9.8m/s 2 on earth Mass how much stuff or matter you are made up of. Mass is also measure of your inertia.

YOUR WEIGHT? ON VARIOUS PLANETS http://www.exploratorium.edu/ronh/weight/

Assignment: Two forks.

Center of Mass: The point in an object where all of its mass balances around. When a force is exerted on an object outside of its center of mass, it will rotate.

Hammer: Center of Mass

Two bodies with the same mass orbiting a common barycenter similar to some asteroids (Antipoe 90) Two bodies with a difference in mass orbiting a common barycenter similar to pluto- charon system Two bodies with a major difference in mass orbiting a common barycenter internal to one body (similar to the EarthMoon system) Two bodies with an extreme difference in mass orbiting a common barycenter internal to one body (similar to the SunEarth system) Two bodies with the same mass orbiting a common barycenter, external to both bodies, with eccentric elliptic orbits (a common situation for binary stars)

Torque Torque is a measure of how much a force acting on an object causes that object to rotate about an axis. Formula = Fr =torque (N-m) F=Force (N) r = distance from axis (m)

Opening a Door Its harder to open a door closer to its hinges. Its easier to open a door far away from its hinges because r is greater and there is more Torque.

EXAMPLES OF TORQUE SEASAWSCROWBARS --Fulcrum

PHET PHYSICS TORQUE SEASAW PHYSICS To balance a seesaw, the torque on one side must equal the torque on the other side. Problem: A 150lb adult sits 4 feet from the center of a seesaw. Where must a 100lb person sit to balance equally? TORQUE

Torque Lab Students will be given a ring stand and clamps, rubber bands and several masses. They set up and sketch the problems on the next page. Use dowels or wood rulers to create a multi- layered balanced torque system.

Place a a 200g mass 10cm from the axis of rotation. Where would you put a 100g mass on the other side to balance it? Place a 200g mass 20cm from the axis of rotation and a 100 mass 10cm from the axis of rotation. Where would you have to put another 100g mass to balance it? Place the mystery mass object 30cm from the axis of rotation.

Torque Problem

Jenga Block Game 1.No glue! Blocks have to be placed and supported entirely by their own weights. 2.Only one block per level. We're making a skewed tower. 3.All blocks are of the same shape, weight, and are of uniform density. 4.Must stand for 30 seconds. 5.2 nd attempt: you may use 10 pennies and two rubber bands.

MOMENTUM

Momentum and Collisions Momentum can be defined as "mass in motion." If any object with mass is moving, then it has momentum p=mv p=momentum (kg-m/s) m=mass (kg) V= velocity (m/s)

Momentum & Collisions! Newtons CradleBilliards

Conservation of Momentum The total momentum of two or more objects before a collision is the same as the momentum of the objects after a collision.

1) Calculate the momentum for the following objects: a)A 75kg speed skater moving forward at 16m/s b)A 135 ostrich running north at 16.2m/s c)A 5.0kg baby on a train moving eastward at 72m/s d)A 48.5kg passenger seated on a train that is stopped. 2) Calculate the velocity of a 0.8kg kitten with a forward momentum of 5kg-m/s. 3) Calculate the momentum of a 6.0kg bowling ball moving at 10m/s down the alley towards the pins.

1.A one kilogram ball traveling at 1m/s hits a another stationary 1kg ball. The ball moving initially stops. What happens to the ball that was originally stationary? 2.A two kilogram ball moving at 2m/s hits a stationary 1.5 kg ball. After the collision the two kilogram ball is moving at 1m/s. How fast is the 1.5kg ball moving? 3.A toy car with a mass of 0.5kg is moving with a velocity of 3m/s and it smashes into and sticks to another car with a mass of 1kg. What is the velocity of the cars after the collision?

Momentum A 500kg canon at rest fires a 10kg ball at 100 meters per second. What happens to the canon?

Work Energy is the ability to do work. Work is the amount of force used to move an object a given distance. Formula for Work is W = Fd F = force in Newtons d = distance in meters. The unit for energy and work is the joule.

Working Hard or Hardly Working Energy is the ability to do work. Work is the amount of force used to move an object a given distance. Formula: W = Fd F = force in Newtons d = distance in meters. The unit for work is the joule.

Lifting Objects: Work done against gravity W = mgh Height object raised (m) Gravity (m/sec 2 ) Work (joules) Mass (g)

Mr. Sapone who is super awesome and super strong deadlifts a 220kg barbell a total distance of 0.7meters before dropping it. How much work did he do?

If you carry a 800N could 10 meters across a room, how much work did you do?

If you carry an object at a constant velocity you do no work on the object because there is no net force in that direction. You might be tired but you didnt do any work.

Two cases: No work done.

A crane uses an average force of 5,200N to lift a girder 25m. How much work does the crane do on the girder? An apple weighing 1N falls distance of 1m. How much work is done on the apple by the force of gravity? A bicycles breaks apply 125N of frictional force to the wheels as the bike moves 14.0m. How much work do the breaks do? A mechanic uses a hydraulic lift to raise a 1,200kg car 0.50m off the ground. How much work does the lift do on the car?

Work against gravity: W=mgh 1A crane lifts a steel beam with a mass of 1,500 kg. Calculate how much work is done against gravity if the beam is lifted 50 meters in the air. 2How much time does it take to lift the beam if the motor of the crane can do 10,000 joules of work per second?

Power Power is the rate at which work is done. Power is work divided by time. P = W/t (J/s) 1 J/s = Watt

P = W/t W = Fd P = Fd/t 746watts is one horsepower

Power Problems

Quick Lab: Calculate your Power 1.Convert your body weight into Newtons by dividing by ~4.5_____ 2.Measure the time it tales you to run up the steps in seconds ____ 3.Measure the height in cm of one step____ and multiply that by the total number of steps____ to get the total height ________. Convert that into meters by dividing by 100__________ 4.Calculate your power by multiplying your body weight in Newtons by the height of the steps in meters______ 5.Divide your Power by 746 to convert it into horsepowerc____

Kinetic Energy The energy of motion. KE = 1/2 mv 2 m = mass of the object v = objects velocity

KE Sample Problems A tomahawk missile has a velocity of 250m/s and a mass of 1300kg, calculate its Kinetic energy. A 9mm bullet with a mass of 0.08kg has a velocity of 400m/s, what is its Kinetic energy? Which one has greater kinetic energy? A 1000kg car moving 90Mi/h (40m/s) or a 36,000kg 18 wheeler going 30Mi/h (13.4m/s)

Potential Energy: Stored energy. Elastic Potential Energy U = kx2 (Spring or elastic potential energy) k = spring constant x = distance stretched in meters A stretched spring stores energy

Potential Energy: Stored energy. Gravitational Potential Energy PE = mgh m = mass of object g= gravitational acceleration height from surface in meters

Potential Energy Problems A 60kg woman is in a helicopter at a height of 2500 meters. What is her potential energy? A 0.4kg apple is hanging from a tree 3.4 meters from the ground. What is its potential energy? What height must I raise a 20kg object to in order for it to have 1000 joules of potential energy?

Conservation of Energy Energy is neither created or destroyed. If you cut the object to the left all of its potential energy will turn into kinetic energy before it hits the floor.

Conservation of Energy PE (top) = KE (bottom) http://phet.colorado.edu/en/simulation/energy-skate-park

PE-KE Problems If I throw a 1kg object out of a window 15 meters off the ground. What will its velocity be just before impact? In the figure on the right, label from greatest to least, potential energy and kinetic energy.

PE-KE Lab Student Led Lab

Torque, Momentum, Impulse,, Energy 2-9 is Torque 10-16 is momentum.

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