EXERCISES

1.A ball is rolling across the top of a billiard table and slowly rolls to a stop.How would Aristotle interpret this observation?How would Galileo interpret this?
Galileo would say that the ball comes to rest because the ball seek its natural state to rest.Aristotle would likely have said it comes to rest because of some forces acting on it; likely friction between the ball and table surface and with the air.

2.Why did Galileo used inclined planes to investigate free fall?
Galileo spent a lot of time polishing the ramps he used in his gravity experiments, to minimize variance from friction.

3.Which has the greater average speed during a game: a football, a baseball, or a golf ball? Defend your answer.
A golf ball because it flew freely in the air without friction after it was hit!

4.One airplane travels due north at 300 km/h while another travels due south at 300 km/h.Are their speeds the same? Are their velocities the same? Explain.
The same speed but different velocities because it is on different directions.

5.Charlie drove his car around the block at constant velocity.True or false?Explain.
False because it could move at constant speed but not of constant velocity due to its ever changing direction.

6.Cite an example of something that undergoes acceleration while moving at constant speed.Can you also gave an example of something that accelerates while traveling at constant velocity?Explain.
Earth, constantly accelerating but moving at constant speed.
Sound, accelerates while traveling at constant velocity

7.Can you give an example wherein the acceleration of a body is opposite in direction to its velocity? Do so if you can.
Twanging a stretched rubber band

8.If you were standing in an enclosed car moving at constant velocity,would you have to lean in some special way to compensate for the car's motion?What if the car were moving with unchanging acceleration?Explain.
No because the velocity does not change so is the speed.My travel is so smooth.

9.On which of these hills does the ball toil down with increasing speed and decreasing acceleration.?
Hill number 2.

10.What is the acceleration of a car that moves at a steady velocity of 100 km/h for 100 seconds? Explain your answer.
Acceleration is a measure how much the speed is getting faster or slower.In this case the car is not getting faster or slower so the acceleration is zero.

11.For a freely falling object dropped from rest, what is its acceleration at the end of the 5th second of fall? The 10th second? Defend your answer.First acceleration due to gravity on earth is 9.8 m/s^2(32.2f/s^2) so
v=ta
v=5(9.8)
v=49 m/s

v=ta
v=10(9.8)
v=98 m/s

No matter what specific time you have,the acceleration will always be 9.8 m/s^2 due to earths gravity (unless acted upon by an outside force). So the answer to all the question is 9.8 m/s^2.

12.Suppose that a freely falling object were somehow equipped with a speedometer.By how much would its speed reading increase with its second of fall?
Each second it would get 9.8 m/s^2 faster since the acceleration due to gravity is 9.8 m/s^2.

13.Suppose that the freely falling object in the preceding exercise were also equipped with an odometer.Would the readings of distance fallen each second indicate equal or different falling distances for successive seconds?Explain.
Different.As the speed increases the distance travelled per unit unit of time also increase.

14.When a ball player throws a ball straight up, by how much does the speed of the ball decrease each second while ascending( assume air resistance can be neglected)?By how much does it increase each second while descending?How much time is required for rising compared to falling?
The only force acting on the ball in either case is ( assuming no wind resistance as you state in the problem ) is gravity.
Acceleration (going down)=decceleration (going up) at approx. 9.8 m/s^2
So it will take the same amount of time to fall once it reaches the top as it will to get there and the speed when it returns to the height of the players hand again will be the same initial speed he threw it upwards in the first place.

15.Someone standing at the edge of a cliff throws a ball straight up at a certain speed and another ball straight down with the same initial speed.If air resistance is negligible,which ball will have the greater speed when it strikes the ground below?Explain.
Both hit with the same speed because the both hit the terminal velocity

16.If you drop an object,its acceleration toward the ground is 9.8 m/s2.
If you throw it down instead.would its acceleration after throwing be greater than 9.8 m/s2? Why or why not?
The object would still be accelerating at 9.8 m/s2 but its velocity would be greater due to the force from throwing.Once an object left your hand after being thrown, there is no more acceleration from the arm.

17.In the preceding exercise can you think of a reason why the acceleration of the object thrown downward through the air would actually be less than 9.8 m/s2?
If we consider air friction then the acceleration of an object in free fall is always less than 9.8 m/s2

18.If it will not by air resistance, why would it be dangerous to go outdoors on rainy days?
I think you would not received serious injury,a raindrop does not have enough mass to gain kinetic energy high enough to do more damage than large hail stones.

19.Extend tables 2.2 and 2.3 (which gives values of from 0 to 5 s) to 0 to 10 s, assuming no air resistance.

                     Time                        Velocity                    Distance Fallen
                  (seconds)                     ( m/s)                          (meters)
                        0                               0                                  0
                        1                              10                                 5
                        2                              20                                20
                        3                              30                                45
                        4                              40                                80
                        5                              50                               125
                        6                              60                               180
                        7                              70                               245
                        8                              80                               320
                        9                              90                               405
                       10                            100                               500
                       t                               (10)t                           (1/2)(10)t2

20.In this chapter,we studied idealized cases of balls rolling down smooth planes and objects falling  with no air resistance.If a classmate complains that all this attention focused on idealized cases is valueless because idealized cases simply dont occur in the everyday world,how would you respond?How do you suppose tha author of this book would respond?
The motion of idealized system is far easier to understand.Once that motion is understood--as a first approximation--the motion with friction (such as air resistance) is then easier to understand as a refinement to the first approximation.