# Name Regents Physics

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Name__________________________ Date_____________________

Regents Physics

Unit Packet Contents
Notes 1: Impulse Momentum Concept Development: Momentum (pg 29)
Guided Practice: Impulse Momentum Notes 2: Conservation of Momentum Concept Development: Momentum Conservation (pg 30) Guided Practice: Conservation of Momentum in Explosions Guided Practice: Conservation of Momentum in Collisions

Unit Objectives: Forces / Vectors

At the end of this unit you will be able to: 1. Define the term momentum, and state its SI unit. 2. Solve problems involving mass, velocity, and momentum. 3. Define the term impulse, and state its SI unit. 4. Relate impulse to change in momentum. 5. Solve impulse-momentum problems. 6. State the law of conservation of momentum. 7. Solve problems involving momentum being conserved in explosions. 8. Explain the difference between an elastic and inelastic collisions. 9. Solve problems involving momentum being conserved in collisions. 10. Relate the law of conservation of momentum to Newton’s third law

Text Assignment: Due Friday February 1

Read pages 86 – 99

Do Review Questions

1-18

Do Plug N Chug

19 – 22

Do Think N Explain

24, 26, 29

Remember to write complete sentences and complete thoughts when doing your homework

Ph6_notes1key Name__________________________ Date_____________________
Thought question:

Page 1 of 4
Regents Physics Notes: Impulse/Momentum

 Even though the Volkswagon will suffer greater damage the forces exerted are
_a__c_t_i_o_n___-_r_e__a_c__t_i_o_n__ forces and are therefore equal.  Since the Mack truck possess much greater ______m__a_s__s___ it also possesses more of a quantity
called _m___o_m___e_n__t_u_m___. o Note that this assumes that the VW and the truck have the sames__p_e__e_d______

Momentum
 A vector quantity that is related to the __m__a__s_s___a_n__d__s__p_e__e_d_______ of a moving object  Objects with larger mass have _m___o_r_e__m___o_m___e_n__t_u_m___ than those with smaller mass and equal

velocity

 Objects with greater velocity have ___m__o__r_e_____________ than those with a smaller speed and

equal mass.

momentum

p = mv

Where:

p = momentum m= mass v = velocity

Units for momentum -- _K__g__m___/s_________ (Not same as newtons Kg m/s2)
Example 1: Find the momentum of the following objects: a. A baseball with a mass of 0.25 kg and a velocity of 20 m/s p = mv = (0.25kg) (20 m/s) = 5 kg m/s b. A train with a mass of 90,000 Kg and a velocity of 5 m/s p = mv = (90,000kg) (5 m/s) = 450,000 kg m/s c. A bullet with a mass of 0.100 kg and a velocity of 125 m/s p = mv = (0.100kg) (125 m/s) = 12.5 kg m/s

Ph6_notes1key Impulse
 A __f_o_r_c__e_______ being exerted over a given ___ti_m___e__________.  Causes a change in an object’s __m__o__m__e__n__tu__m_______.

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J  Ft

Where:

J = impulse F = force t = time

Deriving Impulse vs. Momentum relationship Remember Newton’s second Law
Fnet = m a

Which formula defines acceleration? a = Δv / t

Substitute in Newton’s second law with this formula. Check the dimensional analysis (do the units work out?)

Fnet = m Δv / t Fnet t = m Δv
Or

J = Δp

Impulse / Momentum problems
The larger the ____f_o__r_c_e_____ and the greater the _______t_i_m__e____ it is being exerted, the more it will change the _m___o_m___e_n__t_u_m__ of an object

Ph6_notes1key

Page 3 of 4

Example 1: A force of 20 N acts on a 2.0 kg mass that starts out at rest for 10 s. Compute the impulse and the final momentum of the mass. Calculate the velocity of the mass after the completion of the 10 seconds.

F = 20 N m = 2.0 kg t = 10 s

J = F t = Δp J = (20 N) (10s) J = Δp = 200 N s

Δp = m Δv = m(vf – vi) 200 N s = 2.0 kg (vf – 0)

vf = 100 m/s

Example 2: A car that weighs 7840 N is accelerated from rest to a velocity of 25.0 m/s eastward by a force of 1000 N. What was the car’s change in momentum? How long did the force act to change the car’s momentum?

Example 3: A force of 6.00 N acts on a 3.00 kg object for 10.0 s. What is the object’s change in

momentum? What is its change in velocity?

60.0 kg m/s

20.0 m/s

Ph6_notes1key

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Example 4: What force is needed to bring a 1.10 x 103 kg car moving at 22.0 m/s to a halt in 20.0 s.

-1210N

Example 5: A net force of 2.00 x 103 N acts on a rocket of mass 1.00 x 103 kg. How long does it take

this force to increase the rocket’s velocity from 0.0 m/s to 2.00 x 10 2 m/s?

100 sec

Example 6: A car weighing 15680 N and moving at 20.0 m/s is acted upon by a 6.40 x 102 N force until

it is brought to a halt.

1600 kg

a. What is the car’s mass?

32000 kg m/s

b. What is its initial momentum?

32000 kg m/s

c. What is the change in the car’s momentum?

50.0 seconds

d. How long does the braking force act on the car to bring it to a halt?

Ph6_CDMntmIntroKey Name ______________________ Date ____________

Page 1 of 1 Regents / Honors Physics

Concept Development: Momentum Intro

Name____________________________________ Date_________________________

Regents Physics

Guided Practice: Impulse / Momentum

1. A fullback of mass 120 kg traveling at 20.0 m/s collides with another player and comes to rest in

1.5 seconds. What was the force of the impact?

1600 N

2. A golf ball of mass 0.050 kg acquires a speed of 80.0 m/s when hit with a force of 3.0 x 103 N.

How long was the club in contact with the ball?

1.3 x 10-4 s

3. What force, acting for 1.35 x 10-3 seconds, will change the velocity of a 95-gram baseball from

50.0 m/s eastward to 45.0 m/s westward?

6.7 x 103 N

4. A 10,000-kg freight car is rolling along a track at 3 m/s. Calculate the time needed for a force of

1000 N to stop the car.

30 s
MomentumForceVelocityMassChange