Projectile Motion — Launch a Ball and Measure Its Flight

Throw a ball and it does two things together: it moves steadily sideways and it falls under gravity. Galileo realised these two motions are independent and simply add up, and the result is always a curved path called a parabola. You will launch a ball and measure it.

Simplest version: let a ball roll off the edge of a table so it leaves flat and horizontal. Measure the table height with a tape measure, and tape a sheet of paper on the floor where you think it will land to mark the spot. For an angled launch, prop a ramp at a measured angle (use a protractor) and note the angle.

Send the ball off the edge the same way several times and mark each landing spot — carbon paper or flour on the floor records the exact points. Measure the horizontal distance from directly below the launch to the landing marks and average them. Try launching faster and slower and watch the distance change while the drop stays the same.

What your launches show. (1) The sideways and downward motions are INDEPENDENT — a ball that dribbles slowly off the table and one that rockets off fast hit the floor at the same moment, because their sideways speed does nothing to their falling. (2) For a launch at an angle, the range is largest at 45 degrees, and any two angles that add to 90 (like 30 and 60) land in exactly the same place. (3) Air resistance bends real trajectories away from a perfect parabola, which is why a golf ball is dimpled and a cannonball is not a bad approximation. (4) The same physics governs a basketball's arc, a fountain's spray, a long-jumper's flight — and, pushed to orbital speed, the parabola curves right around the planet and becomes an orbit.