Projectile Motion

Projectile Fired Horizontally

A cannonball shot from a cannon, a stone thrown into then air, a ball rolling off the edge of table, a spacecraft circling the earth – are all examples of projectiles.

Projectile: an object that moves through space acted upon only by the earth's gravity.

The shape of a projectile’s path is known as a parabola.

For projectiles, vertical motion and horizontal motion are not related and should

be treated separately.

For projectiles, vertical motion and horizontal motion are not related and should

be treated separately.

For projectiles, vertical motion and horizontal motion are not related and should

be treated separately.

The horizontal component of motion for a projectile is just like the horizontal motion of a ball rolling freely along a level surface (ignoring friction).

It moves with a constant velocity.

0s 1s 2s 3s 4s 5s

0m 1m 2m 3m 4m 5m

The ball moves an equal distance per equal interval of time.

There is no horizontal force to cause it to accelerate after it has been set in motion.

0s 1s 2s 3s 4s 5s

0m 1m 2m 3m 4m 5m

The same is true for a projectile – when no horizontal force acts on the projectile, the horizontal velocity remains constant.

0s 1s 2s 3s 4s 5s

0m 1m 2m 3m 4m 5m

The vertical component of the projectiles motion is just like the motion of an object in freefall.

0s

1s

2s

3s

4s

0m

5m

20m

45m

80m

In the vertical direction, there is a force involved – the force of gravity, g.

Therefore, there is an acceleration in the direction of the force – down.

0s

1s

2s

3s

4s

0m

5m

20m

45m

80m

So, the ball’s velocity changes with time.

0s

1s

2s

3s

4s

0m

5m

20m

45m

80m

Most importantly, the horizontal and vertical

motions of the projectile are not

related

The vertical motion involves acceleration.

Vertical motion

The horizontal motion deals with constant

velocity.

Vertical motion

Horizontal motion

A projectile is a combination of both

motions.

Vertical motion

Horizontal motion

A projectile is a combination of both

motions.

Vertical motion

Horizontal motion

A projectile is a combination of both

motions.

Vertical motion

Horizontal motion

A projectile is a combination of both

motions.

Vertical motion

Horizontal motion

PROJECTILE MOTION

dx = 5m

t = 4s

dy = 80m

A soldier shoots a cannonball out of a cannon horizontally from the top of a cliff. At the same moment, another soldier drops a cannonball straight down from the same

height. Which cannonball strikes the ground first?