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Beating the Train
Activity Description
Learning Goals
- Use Newton's 2nd Law to accurately predict changes in motion of macroscopic objects ( HS-PS2-1)
- Use kinematic equations to determine the necessary acceleration to move an object
- a certain distance
- for a certain amount of time
Prior Knowledge Required
- Units
- Dimensional Analysis
- Kinematic Equations
- Newton's 2nd Law of Motion
- $F=ma$
Code Manipulation
- Modify existing code
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Activity
Handout
Beating the Train A train is approaching a crossing, traveling at a constant velocity if 15 m/s to the east. You are on an afternoon ride on your motorcycle when you get stopped at a stoplight 50 m south of the crossing. At the instant the light turns green, the train is 90 m west of the crossing. Your mass, including the motorcycle, is 400 kg
- Determine the amount of time required for the train to reach the crossing.
- Using the time found in #1, determine the minimum acceleration required for you and your motorcycle to beat the train and safely cross to the other side.
- Given a frictional force of 100 N that opposes you as you accelerate to the train crossing, what is the minimum force exerted by the motorcycle that is necessary to miss the train?
- Modify the Colliding Crates program to fit this scenario.
Code
GlowScript 2.7 VPython #Creating the objects floor = box(pos=vector(0,-30,0), size=vector(100,4,12), color=color.white) #I've created the floor that the crate will slide across crate = box(pos=vector(0,0,0), size=vector(20,20,5), color=color.red) #I've created the crate, along with its dimensions and initial position resting on the floor #Setting the time interval t=0 #I've set the initial time to zero. tf=0.940 #I've set the final time to 0, which gives the crate enough time to slide across the floor dt=0.01 #I want my time interval set at 1/100th of a time unit #Creates velocity vectors as a function of time get_library('https://rawgit.com/perlatmsu/physutil/master/js/physutil.js') #The program needed to know what a motion map is defined as motionMap = MotionMap(crate, tf, 5, markerScale=0.1) #I want to display 5 arrows showing the motion of the crate #Giving the objects an initial velocity cratev=vector(75,0,0) #I'm defining the constant velocity of my crate to be 75 in the x-direction(left to right) while crate.pos.x<35: #I want the crate to stop before it slides off the floor rate(50) #This rate can speed up or slow down the replay crate.pos=crate.pos+cratev*dt #I'm moving the crate by adding the change in position (cratev*dt) to the previous position (crate.pos) t=t+dt #I'm updating the time #This updates the velocity vectors motionMap.update(t,cratev) #This updates the motion map and display of the arrows as the crate slides across the floor #This creates the graph of the kinetic energy of the crate #f1 = gcurve(color=color.blue) #Setting up a graph to show the kinetic energy of the crate as a function of time #for t in arange(0, 0.94, 0.01): # Time goes from 0 to 0.94 in 0.01 time intervals # f1.plot(pos=(t,cratev.mag**2))