UNIT 2 Two Dimensional Motion And Vectors

ConcepTest 3.5 Dropping a Package 1) quickly lag behind the plane while falling 2) remain vertically under the plane while falling 3) move ahead of the plane while falling 4) not fall at all You drop a package from a plane flying at constant speed in a straight line. Without air resistance, the package will: [CORRECT 5 ANSWER]

ConcepTest 3.5 Dropping a Package 1) quickly lag behind the plane while falling 2) remain vertically under the plane while falling 3) move ahead of the plane while falling 4) not fall at all You drop a package from a plane flying at constant speed in a straight line. Without air resistance, the package will: Both the plane and the package have the same horizontal velocity at the moment of release. They will maintain this velocity in the x-direction, so they stay aligned. [CORRECT 5 ANSWER] Follow-up: What would happen if air resistance is present?

ConcepTest 3.6b Dropping the Ball II 1) the “dropped” ball 2) the “fired” ball 3) neither – they both have the same velocity on impact 4) it depends on how hard the ball was thrown In the previous problem, which ball has the greater velocity at ground level?

ConcepTest 3.6b Dropping the Ball II 1) the “dropped” ball 2) the “fired” ball 3) neither – they both have the same velocity on impact 4) it depends on how hard the ball was thrown In the previous problem, which ball has the greater velocity at ground level? Both balls have the same vertical velocity when they hit the ground (since they are both acted on by gravity for the same time). However, the “fired” ball also has a horizontal velocity. When you add the two components vectorially, the “fired” ball has a larger net velocity when it hits the ground. [CORRECT 5 ANSWER] Follow-up: What would you have to do to have them both reach the same final velocity at ground level?

Projectiles: Launch At Any Angle Monday September 26 Projectiles: Launch At Any Angle

TODAY’S AGENDA UPCOMING… Projectile Motion Monday, September 26 Projectile Motion Mini-Lesson: Launch At Any Angle Hw: Complete Practice D Problems (all) UPCOMING… Tues: LAB 3: Projectile Motion Wed: More Projectile Motion Thurs: Problems @ the Boards Fri: Problem Quiz 2 Projectile Motion Access to Reading Quizzes ENDS @ 11:30pm Mon: Problems @ the Boards Tues: CH 3 TEST

Demonstration with MythBusters Demonstration with Dr. Walter Lewin

General Launch Angle

General Launch Angle

Resolving the Velocity

Resolving the Velocity

Projectile Motion Equations Horizontal Velocity Eq 2 Vertical Velocity Eq 3 Eq 4 Horizontal Displacement

Projectile Motion Equations Vertical Displacement Eq 6 Range Eq 7 Time to the Top

Consider the Range equation: Sample Problem A golfer hits a golf ball at an angle of 25.0˚ to the ground. If the golf ball covers a horizontal distance of 301.5 m, what is the ball’s maximum height? (Hint: At the top of its flight, the ball’s vertical velocity component will be zero.) Consider the Range equation: Solve for the Now find time to the top:

Find the vertical height at 2.68 s:

Sample Problem A potato is shot from a potato gun at 100.0 m/s at an angle of 45.0˚. The potato is shot from a bridge 50.0 m above the water. Find the following: a) total time of flight b) final velocity just before hitting the water c) total horizontal displacement d) maximum vertical displacement above the water

Break the initial velocity into x- and y- components. What must I do first? Break the initial velocity into x- and y- components. Which question is easiest to answer? Find the total time of flight Which equation has all the information but time? By quadratic equation, t = 15 s

Without the quadratic formula solve for t: 2 STEPS: Find final velocity in y-axis Find time

What is the final velocity?

What is the total horizontal displacement? What is the maximum vertical displacement above the water?

Sample Problem .82 s

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