Workshop › Pool › Step 9 of 33

A shot is a velocity

What we are doing

A shot gives the cue ball a velocity: a speed, power, in the direction aim. The same cos and sin split it into the two parts the position needs, vx and vy. Space shoots.

```js
let power

  power = 8

function shoot() {
  cue.vx = Math.cos(aim) * power
  cue.vy = Math.sin(aim) * power
}

  else if (event.key === ' ') shoot()
```

What it means

• power is 8 at the start: 8 pixels per frame.
• vx and vy are the parts of the speed along x and y. At aim = 0 the shot is vx = 8, vy = 0.

Your turn

1. Under let aim ... write let power; in reset, under aim = 0, write power = 8.
2. Under reset, leave an empty line and write shoot.
3. In the key listener, add the Space line above else return.

Skills: Velocity and gravity

← Turn the aim Roll →

All steps

1. The room
2. The table
3. The cue ball
4. Draw the balls
5. The rack
6. Numbers on the balls
7. An aim line
8. Turn the aim
9. A shot is a velocity
10. Roll
11. Friction
12. Cushions
13. Aiming and rolling
14. Hide the aim while rolling
15. Count the shots
16. Balls that touch
17. Swap the push
18. Six pockets
19. In the pocket
20. Scratch
21. Balls left
22. Clear the table
23. Choose the power
24. A power bar
25. A slingshot
26. Press to aim
27. Pull back and let go
28. Smaller steps
29. Predict the hit
30. Draw the ghost ball
31. Where the hit ball goes
32. Your best
33. Build it yourself: two players