Phsyics Kinematics: cannonball shot straight up

In summary, the ball will miss the target by more than 960 meters. The options for the distance traveled vary depending on the angle at which the ball is dropped.
  • #1
61
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http://www.screencast.com/users/trinhn812/folders/Jing/media/5c3b51ea-aed8-4321-964c-126b49a3c1dc

F/m = 0.3m/s^2
distance in x direction= 1/2(a)(T^2)

By placing v(y) =0 and v(initial)=100 I found the time to be 20 sec.
But my answer is 60m. So 1020-60=960m

Wouldn't the ball misss the target by more than 960 meters? Why are the options ranging from 15-60. Perhaps I'm missing the point here. The acutal answer is 31.2
 
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  • #2
okgo said:
http://www.screencast.com/users/trinhn812/folders/Jing/media/5c3b51ea-aed8-4321-964c-126b49a3c1dc

F/m = 0.3m/s^2
distance in x direction= 1/2(a)(T^2)

By placing v(y) =0 and v(initial)=100 I found the time to be 20 sec.
But my answer is 60m. So 1020-60=960m

Wouldn't the ball misss the target by more than 960 meters? Why are the options ranging from 15-60. Perhaps I'm missing the point here. The acutal answer is 31.2

here is my math for it.

[tex]v_{y}=v\sin\theta[/tex]
[tex]v_{x}=v\cos\theta[/tex]

[tex]t=\frac{v\sin\theta}{g}[/tex]
to get the total time in the air multiply by two, becuase that time is only half way.
[tex]x=v\cos\left(\theta\right) t[/tex]
plug in t
[tex]x=\frac{2v^2\sin\theta \cos\theta}{g}[/tex]

that should get you the distance traveled... i think but look over my math.
 
  • #3
Oh. I'm having trouble with the angle though. Not sure what it would be.
 
  • #4
and isn't there acceleartion in the x direction too?
 
  • #5
okgo said:
Oh. I'm having trouble with the angle though. Not sure what it would be.

okgo said:
and isn't there acceleartion in the x direction too?

From what i saw in the problem there were not any more forces than just gravity... and gravity only works in the y direction. your angle is the one given in the problem, 45.
 
  • #6
Oh I was talking about question 23. Hehe I already solved for question 22. Oh well. My exam is in 20 min. Dumdumdum. So it's okay. Thanks for the help though
 

1. What is kinematics in physics?

Kinematics is the branch of physics that deals with the motion of objects without considering the causes that led to that motion. It involves the study of the position, velocity, and acceleration of an object, as well as how these quantities change over time.

2. How does a cannonball shot straight up move?

When a cannonball is shot straight up, it experiences an initial upward velocity due to the force from the cannon. However, this velocity decreases as the ball moves against the force of gravity. Once the ball reaches its maximum height, its velocity becomes zero and it starts to fall back to the ground.

3. What are the key equations for kinematics?

The key equations for kinematics are the equations of motion, which include:

  • Position (x): x = x0 + v0t + 1/2at2
  • Velocity (v): v = v0 + at
  • Acceleration (a): a = (v - v0) / t

where x0 is the initial position, v0 is the initial velocity, t is time, and a is acceleration.

4. How is the motion of a cannonball shot straight up affected by air resistance?

Air resistance, or drag, affects the motion of a cannonball shot straight up by slowing it down as it moves through the air. This means that the ball will not reach the same maximum height as it would without air resistance, and it will also take longer to fall back to the ground due to the opposing force of air resistance.

5. What is the importance of studying kinematics in physics?

Studying kinematics is important in physics because it allows us to understand and predict the motion of objects. This knowledge is crucial in many fields, such as engineering and astronomy, where precise calculations of motion are necessary for designing structures or predicting the movements of celestial bodies.

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