Posted by **poi** on Friday, January 27, 2012 at 5:55pm.

a cannonaball is fired stright up into the air at a speed of 80 ft/sec from a height of 2ft. A. when will the cannon ball be 98 ft in the air?

B. when will the cannonball hit the ground?

- algebra -
**Damon**, Friday, January 27, 2012 at 6:11pm
Vi = + 80

g = -32 ft/s^2 (old text, have not seen these units for years)

h = 2 + Vi t - (32/2) t^2

98 = 2 + 80 t - 16 t^2

16 t^2 - 80 t + 96 = 0

t^2 - 5 t + 6 = 0

(t-2)(t-3) = 0

t = 2 or 3 seconds

Two on the way up, three on the way down

When will h = 0 ?

0 = 2 + 80 t - 16 t^2

8 t^2 - 40 t -2 = 0

t = [ 40 +/- sqrt(1600 +64) ]/ 16

t = [ 40 +/- 40.8 ] / 16

negative time was before we pulled the trigger, use + solution

t = 80.8/16 = 5.05 seconds

## Answer This Question

## Related Questions

- science - A cannon ball is fired straight up into the air at a speed of 80 ft/...
- physic - A cannon ball is fired at an angle of 30° above horizontal with an ...
- algebra - Library Assignment When a ball is thrown up into the air, it makes the...
- physics - A cannon barrel is elevated at an angle of 45°. It fires a ball with a...
- physics - A cannon barrel is elevated at an angle of 45°. It fires a ball with a...
- Physics - A cannon barrel is elevated at an angle of 45°. It fires a ball with a...
- algebra - im trying to help my son i have no ida about this stuff any help would...
- Maths - When a ball is thrown up into the air, it makes the shape of a parabola...
- math - When a ball is thrown up into the air, it makes the shape of a parabola. ...
- math - im trying to help my son any help would be great When a ball is thrown up...

More Related Questions