Group: Name(s) Date:
Work in Lifting a Backpack Vertically
You are holding a backpack initially at rest. You then pull upwards lifting the backpack to a new height and end with the backpack again at rest. Your backpack has a mass of 2 kg and is lifted a vertical distance of 60 cm.
1. Predictions
(a) Sketch predictions of the position, velocity, and pull as functions of time. Include the time before you start lifting, and after you are done.
(b) What is the change in kinetic energy of the backpack?
2. Measure: Now do the experiment
(a) Drag the file W115Backpack.xmbl from the server University Physics/TeamPhysics 311/Labpro to the My Documents folder. Connect the Labpro to the computer, a motion sensor to Dig/Sonic 1 and a force sensor to In 1. Be sure that the force sensor is on the 50 N setting. The motion sensor should sit on the floor with a protective cage over it. Open the program.
(b) Calibrate the force sensor. (Experiment/Calibrate/Force Sensor, then click Calibrate Now.) Hold the force sensor vertical and enter 0 N and keep this result. Hang the 2.050 kg mass from the sensor, enter the appropriate force and keep. Click Done and Close.)
(c) Zero the sensors appropriately.
(d) Hold the force sensor vertically above the motion detector, with the 2.05 kg "backpack" attached. Your hand should hold the force sensor. Click Collect, stay at rest for 1 sec, then quickly but smoothly raise the backpack about 40-60 cm and return to rest. Keep your force less than 40 N, so you don't exceed the capabilities of the sensor.
(e) Graphs. Were your predicted shapes for the position-time and force-time graphs correct? If not, sketch what you actually observe and explain the reason for the differences.
(f) Through what vertical distance did you lift the backpack? Use statistics on the position-time graph to answer this. You should have a distance and a standard deviation in the distance.