Question on relative motion and circular motion.

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Homework Help Overview

The discussion revolves around two physics problems related to relative motion and circular motion. The first problem involves a student on a moving train throwing a ball at an angle, while the second problem concerns a race car accelerating on a circular track.

Discussion Character

  • Mixed

Approaches and Questions Raised

  • The original poster attempts to understand how the motion of the ball is perceived by an observer on the ground, questioning the relationship between the train's speed and the ball's trajectory. In the second problem, participants discuss the components of acceleration in circular motion and express confusion over missing information necessary to solve the problem.

Discussion Status

Some participants have provided insights into the nature of acceleration in circular motion, noting the need for additional data to solve the second problem. There is acknowledgment of a similar problem in the textbook, but uncertainty remains regarding the application of that solution to the current context.

Contextual Notes

Participants highlight the lack of specific information regarding the speed of the race car and the radius of the track, which are critical for solving the second problem. The original poster has confirmed that the problems are presented as given in their homework assignment.

SilverLx
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Hey guys, I've been working on this physics for a few hours, and feel like I am just missing a key point. At first I felt that the problem was missing data, until in the same section I found another that I felt the same. Now I feel like I'm missing a concept or two.

The first problem I have having issues with is:

A science student is riding on a flatcar of a train traveling along a straight horizontal track at a constant speed of 10.5 m/s. The student throws a ball into the air along a path that he judges to make an initial angle of 60.0° with the horizontal and to be in line with the track. The student's professor, who is standing on the ground nearby, observes the ball to rise vertically. How high does she see the ball rise?

Now, I see that the train is moving at 10.5 m/s, so although the student throws the ball at the angle of 60.0 degrees to the horizontal, the professor see's the ball's velocity as 10.0 m/s + the vector components at which the student throws the ball? Please guide me in the right direction.


As for my second problem:

A race car starts from rest on a circular track. The car increases its speed at a constant rate at as it goes 7.75 times around the track. Find the angle that the total acceleration of the car makes with the radius connecting the center of the track and the car at the moment the car completes its trip of 7.75 times around the circle.


As for this problem, I am almost at an utter loss. Any help would be greatly appreciated, and I am by no means trying to get answers, just a general push in the right direction. Thanks in advance for your time.
 
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Heh, just an update, finally figured out the first one :). ANy help with the second would be appreciated!
 
anyone :frown:
 
SilverLx said:
As for my second problem:

A race car starts from rest on a circular track. The car increases its speed at a constant rate at as it goes 7.75 times around the track. Find the angle that the total acceleration of the car makes with the radius connecting the center of the track and the car at the moment the car completes its trip of 7.75 times around the circle.
In general, something going in a circle could have both a tangential and radial component of acceleration. However, since you are given no information about the speed of the car or the radius of the track, I don't see how you can solve this one.
 
alright, thanks. In the book there was a similar problem, that asked what's the angle if it goes around once, and they said tan(1/4pi) = 4.55° is the answer. Definitely confused on this one..
 
SilverLx said:
In the book there was a similar problem, that asked what's the angle if it goes around once, and they said tan(1/4pi) = 4.55° is the answer. Definitely confused on this one..
That answer would make sense if the car made it around in one second. Without that additional information, the problem cannot be solved.

Are you sure you are presenting these problems exactly as given?
 
Yeah I am, That's compied an pasted from webassign
 

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