SAT Subject Test in Physics

In summary, the problem involves finding the speed of a projectile of mass 2M when fired from a toy cannon with a force F and initial speed V. The solution involves using the equation F=ma and the fact that the time in the barrel is not the same for both projectiles. By rearranging the equation v^2=2ad and substituting it into F=ma, the correct answer of B) v/sqrt(2) can be found.
  • #1
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[SOLVED] SAT Subject Test in Physics

Homework Statement


Assume that every projectile fired from a toy cannon experiences force F along the length of the barrel. If a projectile of mass M leaves the barrel with speed, V, at what speed will a projectile of mass 2M leave the barrel with?


Homework Equations


F=ma, a=(Vf-Vo)/t


The Attempt at a Solution


The force F, produces acceleration of V/t for mass m, so the same force should produce F=(2m)(v/t), so the velocity equals v/2?

This is a multiple choice question with choices A) v/2, B)v/sqrt(2), C)v, D)2v, E)4v

The book says the answer is B, but gives no explanation.
 
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  • #2
dtl42 said:
The force F, produces acceleration of V/t for mass m, so the same force should produce F=(2m)(v/t), so the velocity equals v/2?
Careful: The time in the barrel is not the same for the two projectiles.
 
  • #3
Oh, that's true, so how can I get around that?
 
  • #4
dtl42 said:
Oh, that's true, so how can I get around that?
How do the accelerations compare? How does final speed (at the end of the barrel) depend on distance and acceleration?
 
  • #5
The final speed is Acceleration/Distance, and we know the distance must be the same for both objects. Can we rearrange the v=a/d and substitute it into F=ma?
 
  • #6
Wait, v doesn't equal a/d, I don't know what I'm thinking...
 
  • #7
Oh, I found out how to do it, just use v^2=2ad and work it out.

EDIT: Sorry for the obnoxious triple post.
 

What is the "SAT Subject Test in Physics"?

The "SAT Subject Test in Physics" is a standardized test administered by the College Board to assess a student's knowledge and understanding of physics concepts. It is often used as an admission requirement for some colleges and universities.

Who should take the "SAT Subject Test in Physics"?

The "SAT Subject Test in Physics" is typically taken by high school students who have completed a rigorous physics course and are planning to pursue a degree in a related field, such as engineering or physical sciences.

What topics are covered on the "SAT Subject Test in Physics"?

The test covers a variety of topics in physics, including mechanics, electricity and magnetism, waves and optics, thermodynamics, and modern physics. It also includes questions on laboratory skills and data analysis.

How is the "SAT Subject Test in Physics" scored?

The "SAT Subject Test in Physics" is scored on a scale of 200-800. Each correct answer earns one point, and incorrect or omitted answers do not result in any deductions. The final score is based on the number of correct answers.

How can I prepare for the "SAT Subject Test in Physics"?

To prepare for the test, it is recommended to review physics concepts and formulas, practice with sample questions and past tests, and familiarize yourself with the test format and timing. Taking a physics course or working with a tutor can also be helpful in preparing for the test.

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