Introduction

The motion of a projectile is governed by the force that launches the object and the gravitational influence on the object as it moves down range. In today's lab, you will launch a projectile and use its flight characteristics to measure the acceleration of gravity. Campus Students will be provided with the materials you need to complete the lab (meter sticks, projectiles, and launchers) and a method for recording and analyzing the motion. Online Students will access the PHET Projectile Motion simulation provided through this link.

Part 1: Play around with various projectiles, angles of elevation and Initial speeds (if possible).

Simulations

Click on the Intro window. Be sure the Air Resistance box is unchecked. Check the velocity vectors boxes. Check the Acceleration Vectors box marked Components.

For one given angle and initial speed, what did you notice about the different projectiles?

Leave the cannon on the ground.

For one given initial speed, what angle produced the longest range?

For any setting, which velocity component changed throughout the trajectory?

Which direction did the acceleration vector point and why?

Part 2: You will need to understand the following relationships to complete this successfully: Range Horizontal Velocity = Time of flight Vertical Velocity = Tan(angle)x Horizontal Velocity Vertical Velocity? Gravity = 2 height The last relationship comes from Conservation of Energy. When you consider the vertical component of the velocity as a factor in kinetic energy you find that gravitational potential energy is equal to vertical kinetic energy; mgh = = my2. You find that this relationship is independent of mass and you can solve for "g". Conduct an experiment at each of these angles of 309, 450, and 60. Instructions for the simulation Go back to the original screen for the simulation. Select the vectors window. Be sure to uncheck the Air Resistance box. Leave the Initial Speed and Diameter the same. Check any boxes in the lower settings. Keep the default setting of the Diameter and set the Mass slider to any value. For all experiments Record the angle, range, time of flight, and height for variations in mass. Be sure to include the tangent of the angle you use in the following table. For each experiment, calculate the acceleration due to gravity.For each angle, you will fire the cannon to three different masses. Tan(308) = 0.5774; Tan(450) = 1.00; Tan(609) = 1.7321 Experiment Range Time Height Horizontal Tan(angle) Vertical Accelerati Velocity Velocity on due to Gravity WNH How well have you measured the acceleration due to gravity