The Speeding Bus
In a famous movie, Speed, a speeding bus jumps an unfinished bridge. Is this possible?
Please do not allow the passenger to die horribly!
Construct a model with the following specifications-make sure view | numbers and units are set correctly:
English (pounds) | More Choices Set angles: degrees
• World | Accuracy = accurate
o 2 000 lb Bus (rectangle) (window | properties); 20 feet long and 5 ft high (window | geometry)
o 2 foot radius wheels (window | geometry), axles at the ends of the bus; 200 lbs for each pair of tires
How to attach wheels to the bus body:
Method 1: Create your bus body and wheels;
Line up your wheel on the body; Put a green round pin on the wheel-this connects 2 layers at once.
It’s a good idea to grab your bus with the mouse and move it to make sure the wheel attached.
If not, you may have attached something to the background instead-click on the pin, delete, and try again.
Method 2: Create your bus body and wheels.
Put a gray round pin on the body and another on the wheel.
Now use the shift key to select both with your mouse. Then click Join.
You may want to temporarily anchor the bus body-sometimes the join skews it when attaching things.
• Horizontal velocity Vx for the bus body varied by a control (ft/s)
o Select the bus body – Define | new control | initial X velocity (or right click on the bus)
o Select the title of the control to set its properties from 0 to 200 ft/sec
o In the Vx box for the bus properties you should see Input[ ]
• Using window | appearance give each part aname – e.g. select the rectangle and type bus body
You can also change colors and other features in the appearance window.
o head radius = 0.5 ft; 10 lbs
o trunk 3 ft tall by 1 ft wide; 100 lb
o legs 3 ft by ft 0.5 ft 40 lb total weight
o bottom of head attached to body with “rotational spring” K=1 lb-ft/º
o leg attached to middle of lower body with “rotational spring” K=1 lb-ft/º
o “Seat belt” is a rope attached from middle body body to edge of bus at back of human trunk
o Create two ramps (rectangles) 50 ft by 2 ft
o Use a pin to connect one end of the ramp to the ground
o Use an actuator to move the ramp up and down.
Drag one end of the actuator to the ramp; the other to the ground to make the connection
It should be of type length(window | properties)
o Use a control to change the actuator length – Select the actuator – Define | new control | length)
The control also has properties so you can click on its title and change its range
You can use one control for both ramps if you like – for example if your control is named “Input” you can enter this in the length field of both actuators
o Both ramps should be at the same angle (select ramp; properties to see the angle Φ)
(Change the length of the actuators to get as close to these angles as you can in the ramp properties; then select the ramp to view its angle Φ.)
Your objective is to have a bus and passenger jump a 50 foot wide gap as safely as possible.
Experimentally determine the optimum velocity for safely transporting the passenger for ramp angles of 5º 10º and 20º