Physics Lab: Projectile Motion
Goal: To observe and collect data on the motion of projectiles
- Rubber band or surgical tubing
- Small balls (if necessary, wad up paper and seal inside masking tape or duct tape to make "balls" which won't do much damage on impact).
- Handy helper for observations
- Protractor (or other way to measure angles)
- Launcher (sling shot or other frame which will allow you to stretch the rubber band for slinging your ammo...uh, projectiles). A piece of thick cardboard with pushpins can be used if you don't have any other "Y" or "U" shaped frame.
- AIM YOUR LAUNCHER CAREFULLY. Be sure that anything within range which might be damaged (Ming china, antique furniture, siblings) has been removed. If you are launching inside the house, a freely suspended towel or blanket at the end of your target area will "catch" your projectile if you shoot too hard.
Experimentally (by observation) determine whether either ball (dropped vs. launched) hits the ground first.
- Use the setup in the diagram below, or assemble something similar.
- Level the launch paltform
- Make sure the ball to be dropped can fall freely.
- Practice so that you can launch and drop at the same time.
- Have your observer note when the balls hit the ground. Marbles hitting a hardwood floor make sufficient noise to tell whether the balls hit the ground at th same time.
- Repeat your "experimental" several times and record your observations.
- Does the horizontal distance your launched ball travels make any difference?
Experimentally determine angle necessary to achieve the maximum height and range for a projectile.
- Use a setup similar to that in the diagram below.
- Make multiple launches, extending your rubber band the same distance for each launch (so that the initial force is the same).
- Record the angle of your platform at each trial.
- Determine the angle at which you achieved maximum height.
- Determine the angle at which you achieved maximum range.
Present your data in table format. Estimate the amount of error in your measurements and the range of error in our final calculated values.
Your report should include:
- A detailed description of your equipment and procedures.
- A detailed account of your observations for dropped vs launched balls.
- The data from each launch for range/height determination (trial #, angle, range, height) .
- A plot of angle vs. height reached.
- A plot of angle vs. range reached.
- A calculation of the initial horizontal and vertical velocity, and the magnitude of the velocity vector for each launch.
Height reached, together with the gravitational acceleration constant will allow you to determine how long your ball was falling:
T = sqrt(2 *height/9.8)
The vertical velocity downwards when it hits the ground, Vy = 9.8 * T, is equal to the inital vertical velocity upwards.
Assuming no interference from wind resistance, you can double this for the total time the ball was in the air, and arrive at horizontal velocity:
Vx = distance/2T
You should now be able to determine the linear velocity
V = sqrt (Vx 2+ Vy 2)
for each launch attempt.
[If you have a spreadsheet capable of handling the math, set it up and let the computer do the calculations for you.]
- Do you expect V to be the same in all cases? Explain your reasons.
- A general conclusion about your data, based on your observatons and data, and including remarks on errors based on your velocity vector determinations.
Follow the instructions at the Moodle to post your lab reports where your fellow students can find them.
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