Welcome back Please pick up your schedule from
Welcome back! Please pick up your schedule from the table by the door.
Expectations • Phones will be collected if they are seen. • Cheating will not be tolerated. 1. Working with a classmate is fine 2. Copying another students work will earn you a zero on the assignment. • When I ask for your attention please stop talking and face the front of the class.
Expectations • Late work will earn a 10 point deduction for each day it is late • Late work can only be turned in up to three days late for credit. • Remain in your seats until the bell rings. • Anyone out of their seats before the bell rings will be asked to stay after class. • If you are absent please see me the day you return for any assignments you missed.
Momentum
Momentum: Physics term • Momentum is a physics term that means the amount of motion in a moving body. • The MORE momentum an object has the GREATER the force must be applied to stop it & vice versa • The lesser the momentum the less force must be applied to stop the object.
Momentum Equation • Momentum can be represented in an equation p=mv (use small p, large P stands for pressure!) p is momentum m is mass v is velocity • Momentum is a vector because it has a magnitude and a direction
• So an object’s momentum depends on how big the object is and how fast it is traveling.
Momentum Problems • Momentum (p) = Mass (m) x Velocity (v) • The resulting units for momentum are: • kilogram • meters/second or kg • m/sec Sample problem: Calculate the momentum for a 60 kg student running through the halls at a velocity of 4 m/sec. Include the correct units ! p = mv p = 60 kg • 4 m/sec p = 240 kg • m/sec
Momentum Practice p = mv A deer with a mass of 146 kg is running head on toward you with a speed of 17 m/s. The deer is running south. Find the momentum of the deer. W: mass = 146 kg; velocity = 17 m/s T: momentum (p) F: p = mv = 146 kg x 17 m/s Answer: 2482 kg-m/s to South (2. 5 x 103 kg-m/s, South)
Momentum Practice p = mv What velocity must a 1210 kg car have in order to have the same momentum as the deer in the previous problem? W: mass = 1210 kg; momentum = 2482 kg-m/s South T: velocity (v) F: p = mv => manipulate formula => v = p/m v = 2482 kg-m/s ÷ 1210 kg Answer: 2. 05 m/s, South
Momentum Practice p(total) = p(1) + p (2) + p(n…. . ) A 21 kg child on a 5. 9 kg bike is riding with a velocity of 4. 5 m/s to the northwest. What is the total momentum of the child & the bike? W: mass(child)=21 kg; mass(bike)=5. 9 kg; velocity=4. 5 m/s T: p(total) F: p = m(total) x v => (21 kg + 5. 9 kg) x 4. 5 m/s Answer: 121. 05 kg-m/s northwest How would you calculate the total momentum if you had 2 objects with 2 different velocities?
Impulse • Impulse is a change of momentum in an object. • When you apply a force on an object, you also exert an impulse on it. When something exerts a force on you, it also exerts an impulse on you. Forces and impulses always go together. • Impulse, like force, is a vector.
Impulse Equation • A force must act on an object for a time in order to change its velocity. • Impulse is equal to force multiplied by time. J=Ft J=Impulse F=force t=time The units for impulse is Newton Seconds or Ns
Impulse and velocity • You can get the same impulse by applying a large force for a short time, or applying a small force for a long time.
Impulse and Momentum • An impulse will cause a change in momentum. J = Δp Or Ft = p 2 - p 1 = m 2 v 2 – m 1 v 1
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