PhET Tutorial Projectile Motion Learning Goal To understand

PhET Tutorial: Projectile Motion Learning Goal: To understand how the trajectory of an object deperds on its nitial velocity, and to understand how ait resistance affects the trajectory For this problem use the PhET simulation Projectile Motion. This smidlaion alows you to fire an obiect from a cannon, see its trajectory, and measure ts range and hang time (he amount of sme in the air. LAUNCH SIMULATION ae Start the simulation Press Fire to launch an object. You can choose the object by dicking on one of the objects in the scrol-down menu at top right (a cannonball is not among the choices) To adjust he cannon barrel\'s angle, click and drag on it or type in a numerical value (in degrees). You can also adjust the speed, mass, and diameter of the object by typing in values. Clickng Air Resistance displays settings for (1) the drag coefficient and (2) the altitude (which controls the air density) For this tuitorial we will use an alstude of zero (sea level) and let the drag coelicient be automatically set when the object is chosen. Play around with the simulation. When you are done, click Erase and select a baseball prior to beginning Part A. Leave Air Resistance unchecked Part A First, you will inwestigate purely vertical motion. The kinematics equation for vertical motion (ignoring oir resistance)is given by hereo-0 is the initial poallon (which is 1.2 m above the ground due to the whets of the canon), is the wnital speed and gis he acceleration due to graily Shoot the baseball straight upward (at an angle of 90 ) with an initial speed of 20 m/s How long does it take for the baseball to hit the ground? Express your answer with the appropriate units.

Solution

lets first calculate the time it takes to reach the top

we use

V-U=at

where v,u are the final and initial velocity

since at top final velocity v=0

thus t=-u/-g

=20/10=2sec

total time T=2t

=4sec.