# SAT Physics and A-Level Physics

• monoceros
In summary: When the maximum amount of energy is lost, the coefficient is 0.In summary, In a collision where two objects separate, some kinetic energy is lost, making it an inelastic collision. The given answer to the SAT question is (C) because linear momentum is conserved in an inelastic collision. In the second question, the stone is whirled in a vertical circle and the string will break when the net force on the string is greater than the tension. The diagram shows that the greatest force on the string is at the bottom of the circle, making this the most likely position for the string to break. As for the angular speed, it will depend on the mass and tension of the string, which can be calculated once the
monoceros
Hi, I am currently studying the Cambridge A-Level and I will also be taking the SAT Physics sometime end of this year. I am not too sure which category these belong to, so hopefully they fit in the K-12 level alright. I currently have two questions which have been bothering me past two days, and I stumbled across this community so I thought I'd try asking for help.

I'll start with the "easy" one, a SAT question which I don't quite get:

Two objects move toward each other, collide, and separate. If there was no net external force acting on the objects, but some kinetic energy was lost, then
(A) the collision was elastic and total linear momentum was conserved.
(B) the collision was elastic and total linear momentum was not conserved.
(C) the collision was not elastic and total linear momentum was conserved.
(D) the collision was not elastic and total linear momentum was not conserved.
(E) None of the above.

The given answer to this question is (C). As I understand, in a collision where two objects separate, is an elastic collision rather than an inelastic one? Anyone care to explain why is this so?

As for the next question, a written A-Level Physics one:

A stone of mass m is attached to a string of length r, which will break if the tension in it exceeds Tmax. The stone is whirled in a vertical circle.

(a) draw diagrams showing the forces acting on the stoe when it is (i) at the top, (ii) at the bottom, of the circle.

The angular speed is increased very slowly.

(b) For what position of the stone, relative to the axis of the rotation, is the string most likely to break?

(c) What will be the angular speed when this occurs?

Okay, I have no problems drawing the diagrams for (a), where I have T (tension of the string), W (weight of the stone), N (normal force), and Fc (centripetal force) labeled correctly, I hope.

The problem comes to part (b). I can't actually see where do I start. Here's what I tried figuring out from: that in order for the string to break, the net force must be greater than the tension of the string? Where do I go from here?

As for (c), I think I'd know how to solve this one as I get part (b).

Any help would be appreciated. Thanks in advance.

monoceros said:
The given answer to this question is (C). As I understand, in a collision where two objects separate, is an elastic collision rather than an inelastic one? Anyone care to explain why is this so?
If I'm not totally wrong on this, it's not elastic as kinetic energy is not conserved.
I hate terminology, especially in a foreign language :).

As for the next question, a written A-Level Physics one:

A stone of mass m is attached to a string of length r, which will break if the tension in it exceeds Tmax. The stone is whirled in a vertical circle.

(a) draw diagrams showing the forces acting on the stoe when it is (i) at the top, (ii) at the bottom, of the circle.

The angular speed is increased very slowly.

(b) For what position of the stone, relative to the axis of the rotation, is the string most likely to break?

The problem comes to part (b). I can't actually see where do I start. Here's what I tried figuring out from: that in order for the string to break, the net force must be greater than the tension of the string? Where do I go from here?

As for (c), I think I'd know how to solve this one as I get part (b).
You drew the diagrams. Which of these situations exert the greater force on the string? Which situation calls for higher string tension?

I hope I was of any help :).

The first one explicitly states that KE was lost--this automatically means the collision was inelastic. Just because the two objects separate doesn't mean the collision was elastic; this can also happen in inelastic collisions (but of course with KE being lost, and in the extreme situation the objects being stuck together). Linear momentum is always conserved

monoceros said:
Two objects move toward each other, collide, and separate. If there was no net external force acting on the objects, but some kinetic energy was lost.

As I understand, in a collision where two objects separate, is an elastic collision rather than an inelastic one? Anyone care to explain why is this so?

"Elastic" and "inelastic" are terms that are usually used to represent the ends of the spectrum of possibilities. If the problem makes no qualifying statement you should interpret ineleastic to mean that the objects stick together after the collision, and elastic to mean there is NO loss of energy. In most cases, some mechanical energy is converted into other forms, primarily heat, during a collision. If the energy lost is less than the maximum (sticking together) the objects will separate.

A ball bouncing on the floor is an example of a partial loss of energy. On each bounce the ball bounces to a lower height because some energy is lost in every collision. The ratio of the relative velocities after and before a collision is called the "coefficient of restitution." When no energy is lost, the coefficient is 1.

## 1. What is the difference between SAT Physics and A-Level Physics?

SAT Physics is a standardized test that assesses a student's understanding of basic physics concepts and their ability to apply them to problem-solving. A-Level Physics, on the other hand, is a more comprehensive course that covers a wider range of topics and is typically taken by students in the UK during their last two years of high school.

## 2. Do I need to have taken A-Level Physics to do well on the SAT Physics test?

No, while having a strong foundation in A-Level Physics can certainly be helpful, it is not a requirement for doing well on the SAT Physics test. The test covers basic physics concepts that can be learned through self-study or a high school physics course.

## 3. How should I prepare for the SAT Physics test?

The best way to prepare for the SAT Physics test is to familiarize yourself with the test format and content, and then practice with past papers and official study materials. It can also be helpful to review basic physics concepts and formulas.

## 4. Are there any specific topics that are heavily tested on the SAT Physics test?

While the test covers a wide range of physics topics, some concepts are more heavily tested than others. These include mechanics, electricity and magnetism, and waves and optics. It is important to have a strong understanding of these topics in order to do well on the test.

## 5. Can I use a calculator on the SAT Physics test?

Yes, you are allowed to use a calculator on the SAT Physics test. However, it is important to note that not all calculators are allowed. Only certain types of scientific or graphing calculators are permitted, and they must meet certain specifications. It is recommended to check the official SAT website for a list of approved calculators before taking the test.

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