Advanced Higher Physics 2018-19

Here's a place for anyone doing AH physics to discuss the course, ask questions you're stuck on, share advice for the assignment, and prepare for the final exam :smile:

How's everyone finding it so far?

Reply 1

Hey234

10

An object of mass 0.20 kg is connected by a string to an object of half its mass. The
smaller mass is rotating at a radius of 0.15 m on a table which has a frictionless surface.
The larger mass is suspended through a hole in the middle of the table.
Calculate the number of revolutions per minute the smaller mass must make so that the larger mass is stationary?

how to answer this question?

Original post by Hey234

An object of mass 0.20 kg is connected by a string to an object of half its mass. The
smaller mass is rotating at a radius of 0.15 m on a table which has a frictionless surface.
The larger mass is suspended through a hole in the middle of the table.
Calculate the number of revolutions per minute the smaller mass must make so that the larger mass is stationary?

how to answer this question?

The above picture depicts what the problem is describing.
“An object of mass m₂ = 0.20 kg is connected by a string to an object of half its mass. The smaller mass m₁ is rotating at a radius of r = 0.15 m on a table which has a frictionless surface.”

The tension in the string is due to the weight of m₂ and the centripetal force is provided by the tension to cause m₁ to move in a circular motion of radius r. You should be able to write Newton’s 2^nd law for m₁ and solve for the angular velocity of m₁ to find the number of revolutions per minute.

OP

Original post by Hey234

An object of mass 0.20 kg is connected by a string to an object of half its mass. The
smaller mass is rotating at a radius of 0.15 m on a table which has a frictionless surface.
The larger mass is suspended through a hole in the middle of the table.
Calculate the number of revolutions per minute the smaller mass must make so that the larger mass is stationary?

how to answer this question?

I've moved your question over into the new AH physics thread for this year :smile:

Reply 4

Hey234

10

Original post by Labrador99

I've moved your question over into the new AH physics thread for this year :smile:

Thank you, i couldn't find the new thread for this year.

OP

Original post by Hey234

Thank you, i couldn't find the new thread for this year.

No problem- I just created it :wink:

Reply 6

Hey234

10

During trial firing of Pioneer Moon rockets, one rocket reached an altitude of
125,000 km. Neglecting the effect of the Moon, estimate the velocity with which this
rocket struck the atmosphere of the Earth on its return. (Assume that the rocket’s path is
entirely radial and that the atmosphere extends to a height of 130 km above the Earth

Please don't answer this, I just need a direction of what theory should I think about here and how to approach this question, I think they are talking about impact velocity but that is not mentioned in the curriculum.

Original post by Hey234

Please don't answer this, I just need a direction of what theory should I think about here and how to approach this question, I think they are talking about impact velocity but that is not mentioned in the curriculum.

I thought impact velocity or impact speed is typically found using conservation of energy or sometimes it also needs conservation of angular momentum. I would be very surprised conservation of energy is not covered in a typical A-level physics syllabus. However, not covering conservation of angular momentum is understandable.

As for this problem, you can solve it using conservation of energy. It is like throwing a ball upward and asking you what is the speed at certain height above the ground.

Reply 8

tomctutor

9

I'm still here tomctutor.
I think the above question is simply F= ma= mv^2/r etc, usual circular motion, where 'a' would be g= GM/r^2 but I might be wrong!

(edited 5 years ago)

Reply 9

rittyt

5

Project Help:
I have three measurement uncertainties, two of them are insignificant... Do I still use the Squareroot uncertainty formula with that one uncertainty or do I just use that uncertainty as my main?

OP

How's everyone feeling about the exam? Hope that the projects all got sent away without any issues :smile:

Reply 11

tomctutor

9

Has anyone got any concerns about this years AHPhysics exam?

Reply 12

tomctutor

9

(Original post by rittyt)
Project Help:
I have three measurement uncertainties, two of them are insignificant... Do I still use the Squareroot uncertainty formula with that one uncertainty or do I just use that uncertainty as my main?
No need to use

Unparseable latex formula:

\sqrt

but should state why you are ignoring these quantities, less than 1/3rd ignore.