Classical Physics
3 . Projectile Motion
Objectives:
Students will measure the maximum height H and the range R of a projectile motion.
They will study the effect of the shooting angle on H and R.
Material used:
4 rulers, track, metallic ball, landing track, A4 white paper, red carbon paper, timer + supply, gun
+ protractor.
Theory:
A projectile is an object upon which the only force acting is gravity. There are a variety of examples of projectiles: an object dropped from rest is a projectile (provided that the influence of air resistance is negligible), an object thrown vertically upwards is a projectile (provided that the influence of air resistance is negligible), and an object thrown upwards at an angle is also a projectile (the same assumption). A projectile is any object, which once projected, continues its motion by its own inertia and is influenced only by the downward force of gravity.
By definition, a projectile has only one force acting upon - the force of gravity. If there were any other force acting upon an object, then that object would not be a projectile.
Projectiles can be launched both horizontally and vertically, and they have both horizontal and vertical velocity and horizontal and vertical displacement.1
If a body of mass m moves in a constant gravitational field (gravitational force m.g ), the motion lies in a plane. The maximum height of projection H is obtained as a function of the angle of projection θ:
2
v0
H=
sin 2 (θ )
2g
And the maximum range R is:
2
v0
R = sin (2θ ) g A steel ball is fired by a spring at different velocities and at different angles to the horizontal. The relationships between the range, the height of projection, the angle of inclination, and the firing velocity are determined.
1
http://library.thinkquest.org/27948/projectile.html
1
Lebanese American University
Classical Physics
Fig. 1: Experimental set up for measuring