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Simple Questions Pt1

  1. Dec 1, 2003 #1
    Simple Questions Pt1. These Questions stem from an old exam that i have yet to turn in. It basically easy in some parts, but some questions im not tos confident in because of my bad track record with confidence in my physics work. By the way the reason why I'm posting the great amount of questions is because of my exams returned back to me so that i could look over it and could maybe get some tutoring with it. So here they are:

    True or False:

    7. A child riding a horse on a merr go round moving at a constant speed experiences changing velocity. T

    8. A balloon filled with water is dripped by prankster from an open window. At the end of 2 seconds the water balloon has an instantaneous speed of about 10 m/s2.

    9. The horizantal component of motion of a projectile undergoes acceleration due to gravity.

    10. An object thrown into the air at an angle of 25 degrees will have the same range as if it were thrown at an angle of 65 degrees at the same speed.

    Multiple Choices:

    24. If a flower pot were dropped from a window ledge 200 meters from the ground and another flower pot were horizantally out the window at the same time, which would hit the ground first? (BTW - - I did a physics experiment to this question by placing a coin at the edge of a table and another at a distance behind it and flicking the coin into the other coin and seeing which one his the floor first.) A. Both would hit the ground ath the same time.

    26. Some of the following quantities and some are scalar quantities. Circle those which are vector quantities: I circled velocity, force, and acceleration /other choices: time, speed, distance, volume, and mass.

    27. (A) A ball is thrown straight up in the air. As the ball rises, does its velocity increase, decrease, or remain the same? Does its acceleration increase, decrease, and remain the same? I said both decreae.

    (B) At the top of its path, what is the velocity of the ball? What is its acceleration? Im not sure what their asking, I should assume there asking what is it movement, for that i say the same

    (C) As the ball descends, does its . . ( same ending as question (A))
    For that I say increased for both.
     
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  3. Dec 2, 2003 #2

    HallsofIvy

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    7. A child riding a horse on a merr go round moving at a constant speed experiences changing velocity. T

    That's correct

    8. A balloon filled with water is dripped by prankster from an open window. At the end of 2 seconds the water balloon has an instantaneous speed of about 10 m/s2.

    False- it would be about 2*9.8 m/s2= 19.6 m/s2

    9. The horizantal component of motion of a projectile undergoes acceleration due to gravity.

    False

    10. An object thrown into the air at an angle of 25 degrees will have the same range as if it were thrown at an angle of 65 degrees at the same speed.

    False.

    Multiple Choices:

    24. If a flower pot were dropped from a window ledge 200 meters from the ground and another flower pot were horizantally out the window at the same time, which would hit the ground first? (BTW - - I did a physics experiment to this question by placing a coin at the edge of a table and another at a distance behind it and flicking the coin into the other coin and seeing which one his the floor first.) A. Both would hit the ground ath the same time.

    Yes, neglecting air resistance they would hit the ground at the same time.

    26. Some of the following quantities and some are scalar quantities. Circle those which are vector quantities: I circled velocity, force, and acceleration /other choices: time, speed, distance, volume, and mass.

    Yes, you are correct.

    27. (A) A ball is thrown straight up in the air. As the ball rises, does its velocity increase, decrease, or remain the same? Does its acceleration increase, decrease, and remain the same? I said both decreae.

    It's velocity decreases as it goes up but it's acceleration remains the same: -9.8 m/s2.

    (B) At the top of its path, what is the velocity of the ball? What is its acceleration? Im not sure what their asking, I should assume there asking what is it movement, for that i say the same

    At the top of its path, the velocity has decreased to 0. That's why it doesn't go up anymore! It's acceleration is still -9.8 m/s2.

    (C) As the ball descends, does its . . ( same ending as question (A))
    For that I say increased for both.

    It's SPEED increases but if you are taking positive velocity upward, then its VELOCITY is still decreasing- at that constant acceleration -9.8 m/s2.
     
  4. Dec 2, 2003 #3

    Doc Al

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    I believe the answer to that one should be true. I think the range goes as sin(2θ).
     
  5. Dec 2, 2003 #4

    chroot

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    Doc Al,

    I agree.

    - Warren
     
  6. Dec 2, 2003 #5
    for 27(C) is the acceleration still the same, and how so?

    Simple Questions Pt2

    (A) The Wright brothers' first successful plane flew at a speed of about 60 km/h. If the Wright brothers were foolhardy enought to fly their plane east into a 80 km/h northerly wind, what would be the resultant speed of their plane? (You can use vectors or the Pythagorean Theorem to answer this question. If you use vectors, be sure to indicate your scale and draw the vectors in the space below, If you use the Pythagorean Theorem, be sure to show your calculations.) distance d = speed x time interval (thats as far as i got)

    (B) If the Wright brothers had been traveling south and had a tailwind of 20 km/hr, what would have been their velocity relative to the ground below?Use velocity vectors to express your answer. Be sure to indicate your scale.

    31. A company which specializes in fireworks displays fires a rocket upward in the air with initial velocity components of 50 m/s in the vertical direction and 10 m/s in the horizantal direction.

    (A) After 4 seconds, what will be the vertical velocity of the rocket, assuming that air resistance is negligible? What role does gravity play in determining the rocket's vertical velocity?

    (B) After4 seconds, what will be the horizontal velocity of the rocket, assuming that air resistance is negligible? What role does gravity play in determinding the rocket's horizontal velocity?

    (C) Given your answers to (A) and (B), at the end of 4 seconds, what is the magnitude of the rocket's resultant velocity? Diagram your answer using vectors or show your calculations.

    32. The first people to reach the summit of Mount Everest (Tenzing Norgay of Nepal and Sir Edmund Hillary of New Zealand) climbed the last 400 meters of the ascent in 4 hours (or about 14,000 seconds). Rounding to the nearest hundredth, what was the average speed in meters per second of the last part of their climb? Show your calculations.

    Formula: v = at and d = 1/2at^2 (again, im not sure if thats the correct formula but that as far as i got)

    Calculations:

    33. The summit of Mount Everest is about 9000 meters above sea level. If Tenzing and Hillary had fallen from the peak to sea level, how long would their fall have lasted? Ignore air resistance. You may express your answer as a square rott. Show your calculations.

    Formula:

    Calculations:
     
  7. Dec 2, 2003 #6

    NateTG

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    This is actually a vector addition problem:
    You've got wind at 80 km/h going north and the plane going 60 km/h going east. Since the two are perpendicular you can use a2+b2+c2 to find that the answer is 100 km/h.


    60 km/h airspeed with a 20km/h tailwind. Add the two together to get 80 km/h. The rest of the problem requires some drawing



    v=v0+at=50 m/s + -9.8 * 4 = 10.8 m/s



    10 m/s


    The magnitude is about 14 m/s. This is similar to the Wright brothers problem.



    Distance=rate x time should give you the answer.

    this is the situation to use
    x=x0+v0t+1/2 at2
     
  8. Dec 2, 2003 #7

    chroot

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    By the way Security,

    I really think you should swing by your teacher's office before or after school one day and spend some time getting some additional instruction. Your teacher is paid to help you, after all.

    - Warren
     
  9. Dec 2, 2003 #8
    Problem, Iam Homeschooled
     
  10. Dec 2, 2003 #9

    chroot

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    Ugh. Travesty.

    - Warren
     
  11. Dec 2, 2003 #10
    I understand if you are tired of typing out all these hints and tips.
     
  12. Dec 3, 2003 #11

    ShawnD

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    Maybe you should consider going to a real school. It's easier to get help when the teacher is a parent or something but their help is only as good as their understanding of the material....which is probably no better than your own understanding. In grade 11 and 12 physics, I had very very in depth discussions with the teacher about scenarios of a given principle just to get a better grasp of it. If I had asked those same questions when talking to somebody who did not have a B.Sc. in physics, I would never have gotten any answers. Same thing with chemistry. Many people do not have a good grasp of chemistry so if you ask somebody likes a parent or a friend about something complicated that is not explicitely covered in the textbook, you will never get the answer you are looking for.

    Well how about we find out? Let's see out gravity to 10m/s^2 (make it easier) and set the initial velcity to 10 as well.

    25 degrees

    vertical velocity:
    V = 10sin(25)
    V = 4.226m/s

    time to top:
    Vf = Vi + at
    t = (Vf - Vi)/a
    t = (0 - 4.226)/(-10)
    t = 0.4226s

    round time = 0.845s

    horizontal velocity:
    V = 10cos(25)
    V = 9.063m/s

    d = Vt
    d = (9.063)(0.845)
    d = 7.658m

    65 degrees

    vertical velocity:
    V = 10sin(65)
    V = 9.063m/s

    time to top:
    Vf = Vi + at
    t = (Vf - Vi)/a
    t = (0 - 9.063)/(-10)
    t = 0.9063s

    round time = 1.8126s

    horizontal velocity:
    V = 10cos(65)
    V = 4.226

    d = Vt
    d = (4.226)(1.8126)
    d = 7.660m


    Yep, they're both the same. I must have screwed up the significant digits someplace.
     
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