Bellwork Why don’t you want your egg to bounce for the project? Because, it may hit the hard ground and crack / break.

Today’s Agenda Follow-up on this week’s lab Momentum and Impulse notes Egg Drop Analysis Momentum and Impulse and the Egg Drop Sports Figures Video Next homework assignment

Work and Power Lab Follow-Up 1/10/14

Follow-up Questions (in your notes) How can a large force result in relatively small power? How can a small force result in relatively large power?

Follow-up Questions (in your notes) [Combining Work and Power equations]

Follow-up Questions (in your notes) Force and distance are directly proportional to power Time is indirectly proportional to power

Follow-up Answers (in your notes) If the force is done over small distances and/or a long period of time If the force is done over large distances and/ or a short period of time

Follow-up Answers with values Example: F = 5500 N; d = 0.015 m and t = 3600 s is… P = 0.023 W Example: F = 5.5 N; d = 1500 m and t = 0.36 s is… P = 23,000 W

Momentum and Impulse Notes 1/10/14

Pre-Quiz (8 True/False Questions) Impulses are normally smaller when bouncing takes place. If a net force acts on an object, the object's momentum will change. Momentum is defined as an object's mass times its velocity. If the net external force acting on a system is zero, then the total momentum of the system is zero.

Pre-Quiz Impulse is defined as the force exerted on an object times the time it lasts. Automobile seatbelts are used to lengthen the time of impact in case of a collision. When a baseball player follows through when hitting the ball, the contact time with the ball is longer. The momentum of a large truck at rest is greater then the momentum of bee flying across the room.

Pre-Quiz Answers Impulses are normally smaller when bouncing takes place. FALSE If a net force acts on an object, the object's momentum will change. TRUE Momentum is defined as an object's mass times its velocity. TRUE If the net external force acting on a system is zero, then the total momentum of the system is zero. FALSE

Pre-Quiz Answers Impulse is defined as the force exerted on an object times the time it lasts. TRUE Automobile seatbelts are used to lengthen the time of impact in case of a collision. TRUE When a baseball player follows through when hitting the ball, the contact time with the ball is longer. TRUE The momentum of a large truck at rest is greater then the momentum of bee flying across the room. FALSE

Momentum and Impulse Momentum (vector): An object that is in motion Unit: kg · (m/s) Impulse (vector): The time and amount of force acting on an object Unit: N · s

Momentum and Impulse Impulses change the momentum of objects The longer the force acts on an object the greater the momentum change (following through on a swing) Extending impact times decreases the force (air bags and seat belts)

Momentum and Impulse In a collision, an object experiences a force for a given amount of time that results in its mass undergoing a change in velocity. Impulse = change of momentum F · t = Δ (m · v)

Egg Drop Analysis Individual – everyone needs to do the analysis Due Monday 1/27/14

Save an egg, crack a smile!

Oh no, Mr. Bill!

Momentum and Impulse and the Egg Drop Project F · t = Δ (m · v) You can not change the mass (m) You can not change the velocity (v) But you can try to change the time (t) So, what will this do to the force (F)?

F · t = Change of momentum Egg vs. Tile Floor F · t = Change of momentum

Egg vs. Grass F · t = Change of momentum

F · t = Change of momentum Egg Drop Project F · t = Δ (m · v) Your goal is to maximize the time! F · t = Change of momentum F · t = Change of momentum

Video

Homework IMPORTANT!!! If given the mass in kg you need to find the weight (Fg) of the object! Work and Power Problems Due Tues. 1/14/14