August 29August 29

AP physicsAP physics

In:In:A stone is thrown horizontally with an A stone is thrown horizontally with an

initial speed of 10 m/s from a bridge. initial speed of 10 m/s from a bridge. If air resistance could be ignored, If air resistance could be ignored, how long would it take the stone to how long would it take the stone to strike the water 80 m below the strike the water 80 m below the bridge?bridge?

a)a) 1 s1 sb)b) 2 s2 sc)c) 4 s4 sd)d) 6 s6 se)e) 8 s8 s

Objective:Objective:

To use 2 dimensions to To use 2 dimensions to understand projectile motion.understand projectile motion.

Success criteria:Success criteria:

Be able to solve projectile Be able to solve projectile problems with horizontal problems with horizontal initial velocityinitial velocity

Projectile motionProjectile motion

Video: Snowmobile Video: Snowmobile projectileprojectile Preliminary runPreliminary run

– I noticed:I noticed: Run 1Run 1

– I noticed:I noticed: Run 2Run 2

– I noticed:I noticed: Run 3Run 3

Horizontal and Vertical Horizontal and Vertical directions are directions are independent.independent.

Horizontal motion has Horizontal motion has constant velocity.constant velocity.

Vertical motion is Vertical motion is freefall motion.freefall motion.

Divide and conquer!Divide and conquer!

HorizontalHorizontal VerticalVertical

Time crosses the line!Time crosses the line!

Practice:Practice:

A ball is kicked with a velocity of 20 A ball is kicked with a velocity of 20 m/s at an angle of 45m/s at an angle of 45oo from from horizontal. horizontal.

What is the horizontal and vertical What is the horizontal and vertical initial velocity?initial velocity?

How high will it go?How high will it go?

How far will it go?How far will it go?

A cannon shoots a cannon ball at A cannon shoots a cannon ball at 18m/s at an angle of 3018m/s at an angle of 30oo from the from the horizontal. What is the distance horizontal. What is the distance the cannonball goes?the cannonball goes?

Wiley Coyote slides Wiley Coyote slides horizontally off a horizontally off a 100 m cliff at 75 100 m cliff at 75 m/s. How far from m/s. How far from the base of the cliff the base of the cliff will he land? will he land?

A bullet shoots from a gun at 200 A bullet shoots from a gun at 200 m/s at an angle of 55m/s at an angle of 55oo from the from the horizontal. How long is it in the horizontal. How long is it in the air? How high will the bullet go? air? How high will the bullet go? How far will the bullet travel.How far will the bullet travel.

A man jumps from a burning A man jumps from a burning building 30 meters from the building 30 meters from the ground. His initial velocity is 10 ground. His initial velocity is 10 m/s at 25m/s at 25oo from the vertical. How from the vertical. How long did it take him to land? How long did it take him to land? How far away from the building should far away from the building should the firemen hold the net?the firemen hold the net?

A tennis player hits a ball from 10 A tennis player hits a ball from 10 meters away from the net that meters away from the net that just barely clears the .75 meter just barely clears the .75 meter net. His initial velocity was 20 net. His initial velocity was 20 m/s. What was the angle he hit it m/s. What was the angle he hit it with?with?

A diver jumps off the 10 A diver jumps off the 10 meter platform with a meter platform with a velocity of 8 m/s at an velocity of 8 m/s at an angle of 55angle of 55oo from the from the horizontal. What were horizontal. What were the horizontal and the horizontal and vertical components of vertical components of her jump. How long her jump. How long does it take her to hit does it take her to hit the water?the water?

Out:Out:

A stone is thrown horizontally with A stone is thrown horizontally with an initial speed of 30 m/s from a an initial speed of 30 m/s from a bridge. Find the stone’s total bridge. Find the stone’s total speed when it enters the water 4 speed when it enters the water 4 seconds later.seconds later.

a)a) 30 m/s30 m/s

b)b) 40 m/s40 m/s

c)c) 50 m/s50 m/s

d)d) 60 m/s60 m/s

e)e) 70 m/s70 m/s