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Projectile Motion – Cliff Problems. Bell Ringer.

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Projectile Motion – Cliff Problems

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Projectile Motion – Cliff Problems

Bell Ringer

• Recall that an object’s motion horizontally and vertically are independent. If I throw a football perfectly horizontally to the right at 5 m/s, what will its horizontal speed be after 1 second, if it hasn’t yet hit the ground? (ignore air resistance)

5 m/s

? m/s

-9.8 m/s

• Everything away except notes if you have them

• No harm in guessing

• 3 Questions

• Good Luck

• Projectile Motion

• Roller Coasters

• Circular Motion

• Momentum

Which of these pictures DID appear in the reading?

a)

• Picture Choice 1

• Picture Choice 2

• Picture Choice 3

c)

b)

Which of these terms was NOT discussed in the reading?

• Projectile

• Parabola

• Centripetal

• Horizontal velocity

Objectives / Announcements

• SWBAT…

• Separate a projectile motion problem into its x and y pieces

• Complete simple cliff-style projectile motion problems

Docket

• Bell Ringer

• Y problem

• X Problem

• Cliff Problems!

Docket

• Bell Ringer

• Y problem

• X Problem

• Cliff Problems!

Do Now

• Recall that an object’s motion horizontally and vertically are independent. If I throw a football perfectly horizontally to the right at 5 m/s, what will its horizontal speed be after 1 second, if it hasn’t yet hit the ground? (ignore air resistance)

Is there anything pushing on the ball horizontally?

No, only gravity pushes on it. If there is no push, speed doesn’t change!

5 m/s

0 m/s

After 0.5 sec

? m/s

5 m/s

After 1 sec

-9.8 m/s

Docket

• Do Now

• Review Topics / Clicker Q’s

• Y problem

• X Problem

• Cliff Problems!

• HW

Projectile Motion Notes

Projectile: An object that moves through space acted only upon by the earth’s gravity.

A projectile may start at a given height and move toward the ground in an arc.

A projectile may also start at a given level and move up and then back down.

Rules

• Projectiles always maintain a constant horizontal velocity (w/o air resistance)

• Projectiles always experience a constant vertical accleration of 9.8 m/s2 downward.

• Horizontal & vertical motion are completely independent of each other.

• For projectiles beginning and ending at the same height, the time it go up = the time it takes to go home.

• Objects dropped from a moving vehicle have the same velocity as the moving vehicle.

Write this down

In projectile problems, you do not need to consider the mass of the object projected. Remember, if you ignore air resistance, all bodies fall at exactly the same rate.

Δdx = vt

The vertical component (y) is a free fall problem

To simplify calculations, the initial vertical velocity, vyi, will be left out of all equations in which an object is projected horizontally.

So,

Δdy = (1/2)gt2

Example 1

In her physics lab, Melanie rolls a 10-g marble down a ramp and off the table with a horizontal velocity of 1.2 m/s. The marble falls in a cup placed 0.51 m from the table’s edge. How high is the table?

Batman flies off of the top of a 19.6 meter building at 7 m/s to the right. How far will he land from the school?

X Problem

Y Problem

Picture

Trig

7 m/s

19.6 m

?

D’andre throws a baseball horizontally from 2 meters off of the ground towards home plate which is 10 meters away. How fast should he throw it so that it lands on the plate?

X Problem

Y Problem

Picture

Trig

vi = ?

2m

10 m

You Try!

X Problem

Y Problem

You are horizontally throwing water balloons at your friend from on top of a ladder. If the person is 18 meters from your ladder, and you can throw at 22 m/s, how high up the ladder should you climb?

Picture

vi = 22 m/s

?m

3.3m

18m