Thrown Ball on Moving Train

In summary, the student is on a train traveling at a constant speed of 12 m/s. They throw a ball at an angle of 53° with respect to the horizontal, observed by the student's TA to rise vertically. To find the height of the ball, the equation (vy)^2=(v0 sin theta)^2-2(g)(y-y0) is used, where vy is the final velocity in the y component, v0 is the initial velocity, g is 9.8 m/sec/sec, and y0 is 0. However, this is incorrect as the initial velocity should take into account the horizontal component of the train's movement.
  • #1
Juntao
45
0
A Physics 111 student is riding on a flatcar of a train traveling along a straight horizontal track at a constant speed of 12 m/s. The student throws a ball into the air on a trajectory that she observes to make an initial angle of 53° with respect to the horizontal along the same line as the track. The student's TA, who is standing on an embankment nearby, observes the ball to rise straight up vertically.

How high does the ball rise in meters?

-----------------------
Of course, I tried this equation, (vy)^2=(v0 sin theta)^2-2(g)(y-y0)
where vy is final velocity in y component
v0=initial velocity
g=9.8 m/sec/sec
y0=0

So if the ball reaches top of its height, its velocity is zero, thus
0=(12*sin 53)^2-(2*9.8)(y)
and I get y=4.69 meters.

Okay, this isn't right, and I'm probably going at this problem the wrong way, right? Argh!
 
Physics news on Phys.org
  • #2
It looks to me like you are assuming vo= 12 m/s and there is no reason to do that. What you are told is that the ball rises vertically relative to the ground. Since the train is moving at 12 m/s, the HORIZONTAL COMPONENT of the ball (relative to the train) must be 12 m/s. Use that to find vo.
(The student is, by the way, throwing the ball opposite to the direction of the train.)
 
  • #3


-----------------------

It seems like you are on the right track, but there are a few things you may want to consider. First, the equation you used is for the vertical motion of the ball, but the train is also moving horizontally. This means that the ball will have a horizontal velocity as well, and its trajectory will be a combination of vertical and horizontal motion. You may want to consider using the equations for projectile motion, which take into account both horizontal and vertical components of motion.

Additionally, it's important to keep in mind that the ball is thrown from a moving train, so its initial velocity will be a combination of the train's velocity and the velocity at which the student threw the ball. This may affect the angle at which the ball is thrown and its initial velocity.

Lastly, it's important to check your units. In your equation, you used a value of 9.8 m/sec/sec for acceleration due to gravity, but the units for this value should be m/s^2. Double checking your units can help ensure that your final answer is in the correct units as well.

I hope this helps and good luck with your problem!
 

1. How does the velocity of the train affect the trajectory of the thrown ball?

The velocity of the train will affect the horizontal component of the ball's trajectory, as the ball will inherit the train's velocity in the same direction. However, the vertical component of the ball's trajectory will remain unaffected by the train's velocity.

2. Will the ball land in the same spot if thrown from the train versus if thrown from the ground?

No, the ball will not land in the same spot if thrown from the train versus if thrown from the ground. This is because the train's velocity will affect the horizontal distance the ball travels before hitting the ground.

3. How does the height of the train affect the trajectory of the thrown ball?

The height of the train will affect the vertical component of the ball's trajectory. If the train is moving at a constant velocity, the ball will experience the same acceleration due to gravity regardless of the train's height. However, the ball's starting height will be higher if thrown from a higher train, resulting in a longer time in the air before hitting the ground.

4. What happens to the ball's velocity when thrown from a moving train?

The ball's velocity will be a combination of its own initial velocity and the train's velocity. The direction of the ball's velocity will also be affected by the direction of the train's velocity.

5. Will the ball's trajectory be affected by wind resistance when thrown from a moving train?

Yes, the ball's trajectory will be affected by wind resistance when thrown from a moving train. This is because the ball will experience a greater relative velocity to the air, resulting in a greater air resistance force that will alter its trajectory.

Similar threads

  • Introductory Physics Homework Help
Replies
6
Views
1K
  • Introductory Physics Homework Help
2
Replies
38
Views
1K
  • Introductory Physics Homework Help
Replies
23
Views
1K
  • Introductory Physics Homework Help
Replies
2
Views
3K
  • Introductory Physics Homework Help
Replies
2
Views
847
  • Introductory Physics Homework Help
Replies
29
Views
6K
  • Introductory Physics Homework Help
Replies
7
Views
2K
  • Introductory Physics Homework Help
Replies
3
Views
1K
  • Introductory Physics Homework Help
Replies
30
Views
3K
  • Introductory Physics Homework Help
Replies
31
Views
3K
Back
Top