Ch2+BensonR

=Section 1= toc 1. Inertia-the natural tendency of an object to remain at rest or to remain moving with constant speed in a straight line. 2. Newton's first law of motion- an object at rest remains at rest, and an object in motion remains in motion with constant speed in a straight-line path unless acted upon by an unbalanced force. 3. In order stop an object from moving at a constant speed, there must be a force acting upon it. 4. A force of friction stops the object from moving which is an unseen force. 5. The greater the mass, the greater the inertia. 6. A frame of reference is important because it describes in what respect and object moves or changes.
 * Checking Up **

Physics to Go 2. 20 cm  5. 7m/s 6. 14.5m/s 7. a)8m/s  b)3.2 m/s c) 5.6 m/s 8. 103 m/s  9. a. 21 cm b. 44 cm c. 58 cm d. 172 cm

=Section 1= Physics to Go 1. Average speed is speed over time and Instantaneous speed is the speed of an object at any given time. 2. a) 240km/h b) 14m/s c) 4.8km/h d) 88.89km/h 3. a) negative acceleration b) positive acceleration c) No d) negative acceleration e) No f) No 4. a)A+ D b)B c)A d)C e) A+, B0, C+ then-, D+ 14.  a) A runner at the halfway point in a 3200m race. b) A runner finishing the 400m race after accelerating to top speed. c) A forward in soccer when the opposing team is in his/her team's territory, jogging to the half field line. d) A runner starting on a starting block in a 55m race. e) A football being caught by a wide receiver.

= Section 3 = What do you see? The first person is moving at a slow pace and the ball is moving slowly. The second person is moving faster and the ball is moving faster. The third person is sprinting and the ball is moving the fastest out of the three. Force is the intangible that makes an object move a certain way. In tennis force exerted on the ball by a racket in order to make a ball move. While serving, one uses all of his/her body weight to wing with as much force as possible making the ball travel quickly. Because of the shape and the mass of the tennis ball it is a lot easier to exceed 100mph than a bowling bowl which weighs 100x more than a tennis ball.
 * What Do You Think?**

1. Newton's second law of motion states an object will change velocity if it is pushed or pulled upon. Acceleration is equal to force over mass. Acceleration is directly proportional to the force. Acceleration is indirectly proportional to the mass. 2. Acceleration is indirectly related to mass. If the mass of an object was to increase, but the force behind the ball decreased, acceleration would decrease.
 * Physics Talk**
 * Summary: ** A qualitative observation is descriptive, things like smell, color, malleability…etc. A quantitative observation is a description of how many. The equation of Newton's second law of motion is acceleration is equal to force over mass (a=f/m). A newton is a unit of measurement that is used to accelerate a 1-kilogram object 1m/s. Newton also say that acceleration is caused by unbalanced forces. The more mass the more force needed to accelerate that object.
 * Checking Up Questions **
 * Physics Talk**
 * Summary ** : Newton's second law states the acceleration is due to unbalanced forces. The force of gravity is also used as weight. In the investigation the ruler was bent by the force of gravity. Weight is calculated by the mass of the object and the force of gravity or w=mg. On earth acceleration due to gravity is 9.8m/s. When a force acts on an object, the object accelerates, but if two opposing but equal forces act on the same object the net acceleration can be 0. Weight is dependent on location while mass is not.

PTG 1) a. 350N (70x 5)  b. 80kg (800/ 10)  c. 10 m/s2 (70/ 7)  d. 80 kg (400/ 5)  e. -15m/s2 (-1500/ 100)  f. -3,000N (100x -30)  3. 42N= (.30)(a); a=140m/s2  4. F= (.040)(20.0); F=.8N  5  a. The reason this is true is the more mass an object has, the more inertia it has. The more inertia it has the more force is needed to make an object accelerate.  b. Mass and acceleration are indirectly proportional. So the less mass the more acceleration, a tennis ball will have more acceleration than a bowling ball, but the bowling ball has more mass. The more acceleration the more it hurts your hand.  9. When a baseball is thrown, your body puts a force on the ball and the ball does not stop until an unbalanced force acts on it…ie the person catching it.  10. 50+ 40= 90 N  11. 200x4= 800 N  12.125N=(.7)(a); a=179m/s2  13. 50^2+120^2=c^2; c=130 NE 67 degrees  14. 4000^2 + 5000^2= c^2; c=6403N going 53 degrees 15. F=am; F=(12.8kg)(9.8m/s2); F=125N 16a. 30^2 + 40^2; c=50 N going 53 degrees 16b. A=50N/5.6kg; A= 8.9 m/s^2 17a] 30^2 +20^2=c^2; c=36N at 34 degrees 17b. A=34N/100kg=.36m/s^2 17c. A=50N/100kg=.5m/s^2

3. 30N is used as a measurement of weight in this situation as it measures the amount of force being put on that object by gravity. 4. On a planet with higher gravity, weight would increase but mass will not.
 * Checking Up Questions **

golf cart, jogger || Rebounding Objects ||
 * Velocity || Acceleration || Examples ||
 * small 1m/s || small 1m/s || 0->1-->2->3->4
 * small 1m/s || big 100m/s || 0->100->200->300->400
 * big || small || Big Truck ||
 * big || big || Airplane ||

1. Newton's second law of motion states acceleration equals force over mass. Therefore it explains how an object will react if pushed or pulled upon. Acceleration=directly proportional to force. Acceleration=indirectly proportional to mass. 2. Acceleration is indirectly related to mass. If you were to throw a medicine ball, it has such a large mass, that it would have a slower acceleration. 1. a2+b2=c2; 125^2+125^2=C^2; C=176.8N 2a.70N-40N= 30N south 2b. 70N south-40N north: 30N due south; a2+b2=c2; 30^2 + 40^2=C2 2500=c2; c=50N South West 2c. Southwest
 * Checking Up Questions **
 * Physics Plus**

Force is the intangible that makes an object move a certain way. In tennis, force exerted on the ball by a racket in order to make a ball move. While serving, one uses all of his/her body weight to wing with as much force as possible making the ball travel quickly. Because of the shape and the mass of the tennis ball it is a lot easier to exceed 100mph than a bowling ball = Section 4 =
 * What Do You Think Now?**

A girl is dropping an apple, creating a strobe picture. The apple is accelerating while traveling vertically downward. The green apple is being thrown outward. The force behind the object is directly proportional to launch speed. If wind resistance is taken into account, the wind could be a factor as well as the mass of the object. The angle of launch is also directly proportional to the maximum distance.
 * What Do You See?**
 * What Do You Think?**

1a. No mater how high you hold the objects, it should stay the same. 2a. They should hit the floor at the same time. 3a. They should still hit the ground at the same time even though the distance has changed. 3b. Yes, the faster the object travels the further it travels. 3c. 4a. It will take less time to reach the target if it starts at a lower height. 5a. The whole time the person is being pushed, it will follow with the person throwing. 6a. The vertical component of a projectile decreases as it travels vertically but increases as it falls to the earth. The horizontal component does not change. 6b. Range is the maximum distance a projectile travels, speed of launch is directionally proportional to the range.
 * Investigate**

Physics Talk
 * Summary ** : Projectiles are a common theme in most sports. Horizontal motion does not increase time in air as illustrated by the horizontally thrown coin and the coin that’s is dropped at the same time. Your first instinct tells you that the frop coin should fall first but this is not the solution as the horizontal component does not affect the vertical component. The two components are completely independent of each other. Acceleration due to gravity is -9.8m/s2.

1. They will hit the ground at the same time because gravity is acting on both objects without wind resistance creating the same acceleration. 2. Vertical velocity is constantly changing because an object will accelerate 9.8m/s due to gravity. 3. At the apex of the throw, the velocity is 0.
 * Checking Up Questions **

11/28/10 1. .. . .  . .  . . 2. ..  . .  . .  ..
 * PTG**

4. A bullet shot will hit the ground at the same time as if it is dropped, many believe this to not be true, but in reality gravity acts on both equally and the x- component does not affect the y- component in any way. 6. Each component of motion is independent of each other. Vertical velocity changes by 9.8m/s while the horizontal component never changes. 7. Without Air resistance, the arrow shot and the arrow dropped will hit the ground at the same time. 8. c=3.6, 33.7 degrees 9a. 11.98m/s 9b. 23.96 m 10a. 8.5m/s 10b. 4.25m

=Section 5=

A girl is kicking a projectile high in the air behind her. As it falls, it lands on another person’s head and bounces into the net.
 * What Do You See?**

Angles impact the direction at which a projectile flies, the bigger the angle the higher it flies. The smaller the angle the more to the ground the ball goes. Also the speed at what it was launched impacts the distance directly. The harder it is launched the further it goes and vice versa.
 * What Do You Think?**

**Summary**: Projectiles act upon two different non-related forces. One being horizontal force and velocity due to the speed and of the launch and the other being downward acceleration which is constantly at -9.8m/s which is not affected by launch. All projectiles are emitted in a parabola shaped arc (air resistance not included) The optimal angle for maximum distance of a projectile is 45 degrees. The smaller the angle the more horizontally it moves resulting in less hang time. The greater the angle the more vertically it moves resulting in more hang time.
 * Physics Talk**

1. Constant downward acceleration and horizontal acceleration. 2. A model must match reality in nature. 3. A 45 degree angle ensures greatest distance. Complimentary angles will result in the same distance traveled.
 * Checking Up **

1. An angle of 45 degrees is the optimal angle for distance if the starting point and ending point is the same. 2a. Once over the angle of 45 degrees, the greater the angle smaller the distance the projectile will travel due to increased hangtime and vertical velocity. 2b. The greater the angle, the greater the range up to and including 45 degrees. 3a 60 degrees produces the same range as a 30 degree angle because they are complimentary angles. 3b. 75 degrees produces the same range as a 15 degree angle, they are complimentary. 4. It is almost impossible to launch oneself at 45 degrees because x velocity> y velocity which means the resulting angle is smaller. 5. He was successful at both events because he got an optimal running start and the perfect from for the optimal arc of a jump. 6a. 9.8m/s^2 DOWN 6b. Vmax=Vix because Vy is 0 at the apex of the projectile. 7a. Vyf=29.4 m/s 7b. Vx after 1 second 5m/s 7c. 15m from the cliff 8. 45 degrees creates maximum distance 9. An angle close to 90 degrees produces the highest projectile trajectory 10a. direction of a= east 10b. d=vit+.5at^2; -100=-4.9t^2; t=4.5 seconds 10c. 90m from the cliff d=vit+.5at^2; d=20(4.5) + .5(0)(4.5)^2 = Section 6 = What do you see? I see a person preparing to push off the wall in a chair with wheels, with his knees bent at a 90 degree angle. He then pushes off the wall keeping his legs straight as he moves away from the wall.
 * PTG**

What do you think? Bend your knees to a 90 degree angle, strain your knees then push up as hard as you can and direct the force towards the floor. The floor will then push up on you....lifting you up into the air.


 * Physics Talk**


 * Summary ** : Newton's third law of motion says for every force there is an equal but opposite force. All forces come in pairs. In a force diagram, all forces are shown acting on an object; in a free-body diagram, it shows all the forces acting on an object each represented by labels and arrows to show in what direction it is acting on. All forces come in pairs, so when you push or pull on an object, that object push or pulls on you with equal but opposite force.

1. Newton's third law of motion says for every applied force, there is an equal and opposite force. AND all forces come in pairs. 2. With an equal force of gravity the mass pulls on the force 3. A free-body diagram shows all the forces acting on an object using arrows to show the direction of the force and every force is labeled.
 * Checking Up Questions **

PTG 1. Yes, but it is equal to the opposite 2. No, but forces balance downward weight 3. A calibrated spring with a needle attached. 4. Fball is too big for the material to hold out, equal but opposite break. 5. The smaller player has bigger acceleration 6. F of boards is equal to -F of player 7. The padding on the hand causes a slower acceleration thus reducing the force on the hand.

What do you think now? Bend your knees to a 90 degree angle and push up as hard as you can and direct the force towards the floor. The floor will then push up on you....lifting you up into the air.

=Section 7=

What do you see? The person is measuring the force needed to pull a shoe on ice and on a rough surface. On the ice he is having an easy time but on the rough surface he is struggling. What do you think? Certain sports have different surfaces they play on and needs for the shoes, this is why the need different shoes. Physics talk **Summary**: Force of friction is between the shoe and the surface. Pulling force=Force of friction, creating a net gain of 0. Normal force is acting on the shoe perpendicular to the bottom of the shoe.

1. The net force is equal to 0 because force of friction=pulling force. 2. The coefficient of friction has no units of measurement because its a force divided by a force. 3. Force of friction is less than the pulling force creating constant speed.
 * Checking Up Questions **

Physics to Go
 * 1) In order to walk around without slipping, you would want to increase friction.
 * 2) When you are ice skating, you do not want to have friction so you can go faster and further on one stride.
 * 3) The ground may have different patches of surface where friction is more than in other places.
 * 4) There is a similar amount of friction on the terrain so they are wearing similar shoes.

7. Air and water have similar effects on motion in the resistance it gives to moving objects. This resistance is similar to sliding friction 8. Even with strong legs and the right shoes, acceleration cannot increase if there is a limit to force. 10. In order to avoid slipping and to have proper traction, friction is a very important force to have. In outdoor sports, people use cleats to better grip the ground to give better footing. 11. On a wet turf field a person wearing soccer flats is dribbling a soccer ball, he makes a sharp cut to the right but falls because he has flat bottomed shoes which do not have sufficient grip to keep his footing. 6. a.w= (1000)(9.8) w= 9,800N b..55=f/9,800 f=5,390 N c. -5390=1000a a=-5.39m/s^2 d.0=Vi+(-5.39)(6) Vi= 32.34 m/s; change in speed e. Originally he was going 32.24 m/s, he claimed he was going 29m/s but this was proved to be wrong. In order to stop in time, he had to stop short causing unneccesary danger to the cars around him. It took him 6 seconds to fully decelerate.

What do you think now? There are many surfaces one can play a sport on, each sport has a different coefficient of friction. So a person needs a different show for each surface because they need to compensate for the difference in the coefficient of friction.

Chapter 7 Investigate

Lab: Bowling with Blocks CP Physics
 * Introduction**: In our last chapter we discussed forces and motion. Newton stated that an object in motion remains in motion unless acted upon by another force. One of the forces that changes motion is friction. Friction opposes motion.

In this experiment we will slide a block of wood across a floor observing both the time and distance in which the object comes to rest.

**Materials**:
 * * Piece of 2x4 (1) || * Stop watch (1) ||
 * * String (.5 m) || * 2.5 Newton scale (1) ||

**Purpose** In this lab you will be measuring the coefficient of friction between a wooden block and the floor. You will work in pairs, but each individual must collect their own data.

=Procedure= **Part I**: Measuring µ 1. Find the weight of the block in Newtons. 2. Place the block of wood on the floor and place a 1-kg mass on top of it. Use a spring scale to find the force needed to pull the block at constant speed. (Hint: make sure to pull the string parallel to the floor.) 3. Repeat 2 more times. 4. Use the problem solving method we went over in class to compute the coefficient of friction between the wood and the floor. 5. Write your µ on the board. 6. What is the percent difference between your value and that of the class average?


 * Table 1** – Friction and Weight

**//m//** || **//% Difference//** ||
 * **Tension (N)** || **Ff (N)** || **Total Weight (N)** || **//m//** || **//Class Average//**
 * 4 || 4.1 || 4 || 4.03333 N || 11N || .366 || .333 || 10.02% ||


 * //Sample Calculations://**

Fx=max Fy=may µ= f/N T-f=max 0 N-W=may 0 µ=4.0333/11 T=f N=W=mg µ=.366 N=11

**Part II**: Chucking the Block 7. **//__Quietly__//** go into the hallway and stretch a 10 m tape along the hall. 8. You are to stand at the “0” and of the tape and your partner is to stand towards the other end. 9. You are to slide your block along the tape as if you were bowling. Be sure to release the block of wood as close to the starting point as possible. 10. Your partner is to record the time that your block is moving and distance it has traveled. Do not throw so hard that it goes past the end of the tape! 11. Repeat the experiment __at least__ three times. Each trial will have different time/distance combinations. This is okay. 12. Switch roles so your partner can gather their data. 13. Use Newton’s Second Law to compute the rate at which the block was slowing. 14. Use the measured distance, calculated acceleration, and the final velocity to find your throwing speed (initial speed of the block). 15. Use kinematics again to find the time it took the block to stop. 16. Repeat for the other trials. 17. Calculated percent error between your measured time and calculated time for each trial.


 * Table** – Friction and Kinematics


 * **Mass (g)** || **Mass (kg)** || **Measured Time (s)** || **Measured Distance (m)** || **Ff (N)** || **Acceleration (m/s2)** || **Calculated vi (m/s)** || **Calculated time (s)** || **% Error** ||
 * 180 || .18 || 2.11 || 5.1 || .05976 || -3.25 || 5.758m/s || 1.772 || 19.074 ||
 * 180 || .18 || 2.18 || 5.8 || .05976 || -3.25 || 6.14m/s || 1.889 || 15.405 ||
 * 180 || .18 || 2.38 || 7.25 || .05976 || -3.25 || 6.865m/s || 2.112 || 12.689 ||

 Sample Calculations: N  Fx=max Fy= may à 0 0.332= (f)/.18 Vf2=Vi2 + 2(a)(d)  F=max N=mg f=.0598 0=Vi2 + 2(-3.25)(5.1) .0598=180a N= .18n 0=Vi2 + -33.15  a=-3.25 W 33.15= Vi2 F Vi = 5.758m/s

-Vi /a=t %error= Abs(calculated time-measured time) Abs(1.772-2.11) -5.758/-3.25=1.772s -- =19.074 Calculated Time 1.772

**Part III**: Questions/Conclusion 1. What does the coefficient of friction in Part I mean? It determines how rough a certain surface is. 2. How does your µ compare to the µ of your classmates? Should your results be the same as everyone else’s in the class? Why or Why not? My µ was only 10% off from the class average. The results should be similar but no the same because the bottom of everyone’s boxes are different plus there might be an error in the measurement. 3. How well did your times agree? Was your percent error high or low? My times agreed to a certain point, the percent error was decent because it was neither lower than 10% nor higher than 20% 4. Does the theoretical physics we are doing in class seem to apply in the real world? Why or why not? Yes it applies when you look at the game of bowling, you can calculate the acceleration and initial velocity of the the bowling ball to find out what you could do to better yourself. 5. Describe at least 3 sources of experimental error. Be specific about how these errors would throw off your results. There could be errors when throwing the box and it hits the measuring tape, if the box bounces from the height it was dropped and the person timing the box is not close to the actual time.

POST THIS LAB ON YOUR INDIVIDUAL WIKI! Your instructor will email you a copy of the class data from Part 1 and this needs to be included as well.

TYPE YOUR CALCULATIONS. Pictures are no longer acceptable: you can use MathType in Word and then insert as a picture, or type directly into the wiki. Either way, be sure to work vertically down the page and leave enough space so that it is easy to understand.

= Section 8 =

What do you think? Each pole is rated for a certain weight, when the length of the pole is increased the spring in the pole is reduced if the weight rating stays the same. It needs to be flexible enough to bend but stiff enough to be able to spring you up.

Investigate Section 8 Pre Lab: deflection of ruler (force, elasticity) length of ruler placement of object mass of object 1. a) How the placement of the penny on a ruler affects the height it is launched.  b) How many cm from the end of the ruler and the height it is launched. c) Ruler and a meter stick d) By making a data table after running multiple tests. Conclusion: The further the penny is from the end of the ruler, the less distance it traveled vertically with the exception of 8 meters from the end of the ruler.
 * Test# || Placement from End of Ruler(In Cm) || Height launched (in Cm) ||
 * 1 || 2 || 72 ||
 * 2 || 4 || 58.3 ||
 * 3 || 6 || 51.6 ||
 * 4 || 8 || 56 ||
 * 5 ||  ||   ||
 * 6 ||  ||   ||

=Section 9= What do you think? No, no matter what you do you will fall down at the same rate as anyone else, its how high up that you jump that matters. Physics Plus 1. a)mgh=1/2 mv^2 +mgh (9.8)(50)=1/2v^2+(9.8)(30) 490=1/2v^2+294 196=1/2v^2 392=v^2 v=19.8 m/s

3. GPEi +Win-Wout=KEf+GPEf (200)(9.8)(25)+200,000J-50,000J=1/2(200)(40)^2+(200)(9.8)(H) 199,000J=160,000+1960H 39000=1960H 19.897m=H