Physical science Tuesday 10-16

Rubric /Answer key

Momentum

Conservation of momentum

Third Law and Momentum example?

Cp Test 2 answers

• Multiple ChoiceTest A Test B

1 D B2 A B3 B B4 C A5 B C6 D A

Cp 2nd test Answers

• Rest of Multiple ChoiceTest A Test B

7 C A8 C C9 A C10 C A11 A B12 D B13 D C

CP Test 2 Answers

• Short Answers

14B, 18AAn object at rest, stays at restAn object in motion, stays at a constant rateUnless a net outside force is applied

15B, 16AThey are applied to different objects, in opposite

directions

CP Test 2 answers

• 16B, 17A

The object would accelerate in a direction different from the direction of the forces

17B, 14A

Tires on roads, Books on tables…

2nd test CP

• 18B, 15A Free body diagrams

Force of gravity

Force of friction Force of ground, engine

2nd test CP

• Problems

• 19B, 20 A

F= 1.125 N

20B, 19A

A= 1.2 m/s2

2nd test CP

• Essay• 21B, 22 A

Without air, both would fall with the same rate of acceleration.

With air, air resistance slows down the rate of acceleration of the feather

22B, 21A

Displacement of ball = 0 , velocity of ball = 0

Answers to 2nd test Honors

• Multiple Choicetest A test B

1 C A2 C D3 A C4 C C5 C A6 A B7 C C8 B C9 C C

Honors Answers

• Multiple ChoiceTest A Test B

10 D B11 A C12 B C13 C A14 D D15 C C

Answers

Short answersA16, B20Free-body diagram

A17, B18Acceleration, in direction not of either force

A18, B16Less friction on smooth sidewalk

Force of ground

Force of gravity

Force of friction

Answers

• A19, B19An object at rest stays at rest, an object in motion stays at constant rate, unless net outside force is applied

A20, B21Gripping rocks while climbing, Traction for MPV car

A21, B17They are equal but opposite, applied to different objects

Answers

ProblemsA22, B23

weight = 42 N

A23, B24acc = 1.2 m/s2

A24, B22Force of friction = 1.125 N

Essay

• A25, B25

– Without air, both objects will be pulled to earth at the same rate of acceleration

A26, B26

Displacement = 0 so velocity = 0 m/s

Discussion of Rubric

For Seat-belt Paper

Homework

• P3631

a. 1200 kg m/s forwardb. 2187 kg m/s northc. 360 kg m/s eastwardd. o kg m/s

2. 6.3 m/s forward

P366

1) For every action, there is an equal but opposite reaction

2) Chair and floor, person and chair, pencil and paper

3) Momentum= quantity of motion = mv

Conservation of momentum = momentum may be transferred in a system but not created or destroyed

P366

4) B

5) The tiny force exerted on the earth by the skier causes an insignificant amount of acceleration by 2nd law

6) 12 kg m/s eastward

p367

1) 4.5 m/s2 east

2) -3,5 m/s2

3) 1,2 m/s2

Momentum, reaction forces and shooting a gun

What force is pushing the rocket upward?

Does the gun gain momentum when it fires a bullet?

Definition of momentum

• What is the momentum of an object?

• How is it calculated?

• How is an object guaranteed not to have momentum?

Change of momentum

• List 3 examples of objects changing their momentum?

• What causes a change in the momentum of an object?

Causes of change in momentum

How does the air-bag in the car affect the change in momentum of the passenger in a car crash?

Force, time and change in momentum. How are they related?

What is the difference in change of momentum?

• Putt-putt golf –vs- hitting a golf ball off the tee

Conservation of momentum

• What does it mean?

• How is momentum conserved during playing pool?

• How is momentum conserved when a sumo wrestler runs into a 6th grader?