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Projectile Motion. The motion of a falling object with air resistance and gravity acting on it. Projectiles. A projectile is any object upon which the only force is gravity Projectiles travel with a parabolic trajectory due to gravity
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Projectile Motion The motion of a falling object with air resistance and gravity acting on it
Projectiles • A projectile is any object upon which the only force is gravity • Projectiles travel with a parabolic trajectory due to gravity • There are no horizontal forces and no horizontal acceleration on projectiles
Projectiles • The horizontal velocity of a projectile is constant • The vertical acceleration of a projectile is caused by gravity and is 9.8m/s/s down • The horizontal and vertical motion of a projectile are independent of each other
Projectile Motion • A force is not required to keep an object in motion • A force is required to maintain acceleration • If a projectile is moving upward there is a downward force and downward acceleration • The object is moving upward and slowing down
Gravity and vertical acceleration • Gravity only causes a vertical acceleration • Gravity does not affect the horizontal distance or motion an object travels • Gravity will affect the vertical distance and motion of an object only
Horizontally launched projectiles • There has to be a horizontal force to cause a horizontal acceleration • A projectile has a constant horizontal velocity and a downward vertical acceleration (deceleration)
Non-Horizontally Launched Projectiles • When the projectile is launched at an angle the path is a parabola • If there was no gravity the projectile would continue upward • no gravity gravity
Vertical Displacement • The vertical displacement of an object can be calculated using: • y = .5 * g * t2 (* = multiplied by) y = vertical displacement g = gravity at -9.8m/s/s t = time in seconds • Use this equation when an object is dropped from rest – it has no initial vertical velocity
Horizontal Displacement • The horizontal displacement of a projectile can be calculated using the following: x = vix * t where x = horizontal displacement in m vix = initial horizontal velocity in m/s t = time in s In this case there is no initial vertical velocity, since the projectile is launched horizontally
Vertical Displacement of an Angled-Launched Projectile • To calculate the vertical displacement of a projectile launched at an angle • y = viy * t + 0.5 * g * t2 • y= vertical displacement in m viy = initial velocity in m/s t = time in s g = gravity, -9.8 m/s/s t = time in s
Sample Problem • A projectile has an initial velocity viy of 19.6m/s and a horizontal velocity of 33.9m/s, what is the vertical and horizontal displacement after 1 s?y = viy * t + 0.5 * g * t2y = (19.6m/s) x (1s) + 0.5 x (-9.8m/s/s) x (1s)2y = 19.6m/s + (-4.9m)y = 14.7m (vertical displacement)x = vix * tx = (33.9m/s) x (1s)x = 33.9m (horizontal displacement)