Physics Web Search: Torque



PHYSICS WEB QUEST: GRAVITYName____________________________________ Date ________________________Go to phet.colorado.eduOpen Gravity Force Lab ()Part I: Force of GravityWhat is true about the force of m2 on m1, and the force of m1 on m2 (two things)?__________________________________________________________________Show the calculation for the force of gravity for the current set up:Set both masses equal to 25 kg, and set them both 4 m apart. You can move the masses and rulers. What is the force of gravity? ___________________ Compare the following answers to this answer.Keep the masses 4 m apart, but change one mass to 50 kg.What is the new force of gravity? _____________________How did it change (compared to #4)? ___________________________________Change the 50 kg mass down to 12.5 kg. What is the new force of gravity? _____________________How did it change (compared to #4)? ___________________________________Set both masses back to 25 kg, but move them so they are 8 m apart.What is the new force of gravity? _____________________How did it change (compared to #4)? ___________________________________Given the two masses of 25 kg 8 m apart, how can you change one mass to get back to the answer in #4? _____________________________________________Now open My Solar System ()Part II: Planetary MotionSelect the preset “Sun and Planet”Set the speed in between fast and accurate Adjust the settings for body 2. Leave the mass = 10, set x position to 150, y = 0, and x velocity = 0, and y velocity = 75.Describe the shape of the orbit. ________________________________________Describe how the planet moves when it is close to the sun. __________________Describe how it moves farthest from the sun. _____________________________Stop. ResetAdjust the settings for body 2. Leave the mass = 10, set x position to 150, y = 0, and x velocity = 0, and y velocity = 200.What happened to the planet? Why? ____________________________________Calculate the escape speed of this planet (assuming distances are in meters and mass in kilograms). This won’t match the simulation as we aren’t given units.Stop. ResetAdjust the settings for body 2. Leave the mass = 10, set x position to 150, y = 0, and x velocity = 0, and y velocity = 80.Calculate the initial moment of inertia for the planet considering it to be a point mass where I = mr2.Calculate the initial angular speed of the system from v = ωrCalculate the initial angular momentum L = IωHit stop when the planet is on the left hand side of the sun.Mouse over the planet and record the x and y components of the planet’s velocity. Use the components to calculate the tangential speed (pythagorean theorem).vx = vy =v = Mouse over the planet and record the x and y components of the planet’s position. Use the components to calculate the actual radius (pythagorean theorem).rx = ry =r = Calculate the final moment of inertia for the planet considering it to be a point mass where I = mr2.Calculate the final angular speed of the system from v = ωrCalculate the final angular momentum L = IωCompare 15 and 21. _________________________________________________Stop. Reset. Click 3 bodies at the bottom of the screen – leave the presets. Click Start.Describe the motion of the blue object relative to the purple planet. ___________ __________________________________________________________________What could this object represent?Stop. Reset. Click 4 bodies at the bottom of the screen – leave the presets. Click Start. Use the tape measure to determine the entire horizontal axis of the purple planet. Divide this value by 2. This is the semi-major axis of the ellipse which represents the radius of the orbit. Purple Radius: ___________Use the tape measure to determine the entire horizontal axis of the green planet. Divide this value by 2. This is the semi-major axis of the ellipse which represents the radius of the orbit. Green Radius: ___________Time one revolution of the purple planet (you may have to reset). This is the period of that planet. Period of purple planet (T): _________________________Use the following formula to approximate the period of the green planet. (Let a = green planet info, and b = purple planet info). Reset and actually time the green planet. What is the measured period? T = ____Is this value close to # 30?Click a few of the other presets to observe some other astronomy phenomena.Now open Lunar Lander ()Part III: Lunar LanderPlay the game. Your goal is to have the maximum number of landings before you run out of fuel. Try to keep the landings soft and avoid the boulders.How many landings did you achieve? ___________________________________What was difficult about this game? ____________________________________ __________________________________________________________________Last Open Torque ( HYPERLINK "" )Part IV: TorqueClick the tab at the top that says torqueSet the force equal to 1 N. Click Go let this run for at least 10 secondsWhat is the torque on the wheel (include direction).What eventually happens to the lady bug? _______________________________From Newton’s second law, a force will cause an __________________________When considering angular motion, a torque will cause an ___________________ ____________________ (consider both torque equations)What must be the centripetal force that keeps the lady bug moving in a circle? __________________________________________________________________Why does this force eventually fail? ____________________________________ __________________________________________________________________Reset all, and set the force back to 1 N.Observe the acceleration vector as you start. Describe how it changes. _________ __________________________________________________________________Will the acceleration vector ever point directly to the center? ________ Why / Why not? (the next steps might help you answer this question) _______________ __________________________________________________________________ Reset all. Set the force back to 1 N.Hit start, wait about 2 seconds, and set the brake force to 1 N. Hit enter and observe.Describe the motion of the wheel: ______________________________________What happened to the acceleration vector? __________________________ Why? __________________________________________________________________ __________________________________________________________________What is the net torque? _________Reset all. Set the Force back to 1 N. Hit Start.After a few seconds, set the brake force equal to 3N and hit enter. Right after you set the break force, calculate the net torque (check with the graph):Eventually the disc stops and the net torque is zero. This is because the breaking torque changed as you can see in the graph. Why did it change? Part V: Moment of InertiaClick the Moment of Inertia Tab at the top.Disregard any millimeter units. They should all be meters.To best see the graphs, set the scale of the torque graph to show a range of 20 to -20.Set the Moment of Inertia Graph to show a range of 2 kg m2 to – 2 kg m2Set the angular acceleration graph to show 1,000 degrees / s2 to –1000 degrees / s2Calculate the moment of Inertia for the disk with the given information.Hold the mouse over the disk so the mouse finger is pointing anywhere between the green and pink circles.Hold down the left mouse button. Move your mouse to apply a force.Look at the graph and try to apply a force that creates a torque of 10.Use the ruler to determine the radius at any point between the green and pink circles. r = ___________mCalculate what the applied force must have been.Calculate the angular acceleration of the disk. Work in SI units, and then convert to degrees / s2. Compare to the graph to check your answer.Predict what will happen to the moment of inertia if you keep the mass of the platform the same, but you create a hole in the middle (increase inner radius). __________________________________________________________________Set the inner radius equal to 2. Calculate the moment of inertia for this shape. Set the disk in motion and check your answer by looking at the moment of inertia graph.Even when the force on the platform changes, the moment of inertia graph remains constant. Why? _____________________________________________ __________________________________________________________________Fill in the blanks: When the mass of an object increases, the moment of inertia ________________. When the distance of the mass from the axis of rotation increases, the moment of inertia ___________________.Part VI—Angular MomentumClick the Angular Momentum tab at the top.Set the scale of the moment of inertia and angular momentum graphs to show a range of 2 to -2.Set the angular speed to be 45 degrees / s.What is the SI unit for angular momentum? ______________________________Calculate the angular momentum in SI units (you should have already calculated the moment of inertia in part II). While the disk is moving, change the inner radius to 2. Observe the graphs.Changing the inner radius automatically changes the angular velocity to 36 degrees / s. Why? (mention moment of inertia and angular momentum in your answer). ................
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