# Projectile Stunt Show

High\-school projectile motion at a night\-time canyon stunt show: independent horizontal and vertical motion, parabolic paths, launch angle and range, and the pull of gravity

By Numa

Topic: Physics & Chemistry

[Open the interactive Jig](https://ask.jig.com/j/aBVUx4SrUDf3)

## Transcript

### 1. The Great Canyon Leap

In 1974, Evel Knievel tried to rocket across Snake River Canyon\. The gold arc was his plan\. His parachute opened at launch, and air drag pulled him down along the red path\. Tonight, a crash\-test dummy makes the jump with no parachute\.

Knievel's paths are scaled to fit this canyon\. He survived with minor injuries\.

### 2. Aim and Power

Drag the barrel to set the angle, and push the lever to set the speed\. Then press the red button, or Fire\! below\. Does the shot reach the net? A label shows how close it lands\.

Mass doesn't matter\. Without air resistance, a heavier dummy follows the same arc\.

### 3. Two Motions at Once

A flying object moves two ways at once: sideways and up and down\. The blue bead shows the sideways motion, in equal steps\. The orange bead shows the height: it rises, slows and falls\. The purple ball has half the sideways speed, yet it stays level with the dummy\.

On the labels, vx is sideways speed and vy is up\-and\-down speed\.

### 4. Gravity Pulls Only Down

In flight, the only force on the dummy is gravity, and it points straight down\. So the sideways speed never changes, while vy drops by about 9\.8 m/s every second\. At the top, vy is zero for an instant, but the dummy keeps moving sideways\.

The show slows time over the top so you can see this\.

### 5. The 45° Rule

Five balls leave the same point at the same speed, at five different angles\. On level ground, 45° goes farthest\. Angles equally far from 45°, like 30° and 60°, land in the same place\. Fire your own shots to compare\.

Air drag makes the best real\-world angle a little less than 45°\.

### 6. Land in the Net

Your turn\. Drag the flag on the far side to where you think the dummy will land\. Set an angle and a speed, then fire\. Too short? Add speed, or move the angle toward 45°\. Too far? Take some speed off\.

Extra challenge: at 23 m/s, two different angles reach the net\. Can you find both?

### 7. Arcs Everywhere

A free throw follows the same rules, and so does a half\-court buzzer\-beater, just faster and longer\. Anything thrown, kicked or launched follows this curve, called a parabola, until air or ground gets in the way\.

The longest human\-cannonball flight on record is 59\.05 m\.