A Projectile from a Cliff

Practice Quiz 3 # 10• A cannon is at the top of a cliff, 150 meters

high. The cannon fires a shell at an angle of 20° above the horizontal. The speed of the shell is 300 m/s as it leaves the muzzle of the cannon. How far from the base of the cliff does the shell land?

• v1 = 300 m/s

• v1x = 300 cos 20° = 282 m/s

• v1y = 300 sin 20° = 103 m/s

Time to Top of Trajectory

• Horiz Vert• v1 282 103• a 0 −10• v2 282 0

• t = (v2 − v1)/ a = 10.3

• 282 51.5 v̄�• s t=2890 t=676v̄�∙ v̄�∙

To the Top

• Doubling

Two Students

• Time from top to ground ?

• s = v1t + ½at2

• − 876 = 0 + ½ (−10) t2t2 = −876 / (−5) = 175.2

t = √175.2 = 13.3

The Whole Trip

• Horizontal Calculation• sx = t = 282 23.6 = 6653 metersv̄� ∙ ∙