Thank you

[candice]

Hi!

I would just like to say thank you vry much to terik and shijun for their help and advice with my project. I did look up what you suggested, and I thank you for your advice.

Shijun, I didn't get to ask my teacher about the marshmellow thing however, so if you could explain that to me yourself that would be fantastic, and I would be really grateful.

Terik, I downloaded that book, thanx! Is there any way I can use that information about the craters formed in reality and link it to how my craters formed? Because I couldn't make craters with meteors of huge speeds like they occur naturally

Does anybody know if there is a relationship between the sine of an angle of a right angled triangle, and the hight? Because when I made my slopes I think I noticed that the angle of the triangle was equal to the height
Could this be so? I kept the hypotenuse at 1 metre

Thanx again, and any more help would be much appreciated!

[deleted-2131]

Candice,

The infomation in the book applies universally. Lots of the same physics will still apply, even if the speed is not so fast. The formation of the craters will be essentially the same. The only information that you will not be able to apply is the information on the chemical and mineralogical changes that occur during natural impact. If you have any more questions, just ask.

It is not clear exactly waht you want to know about the sine and the height. Do you want to know how the sine of a right traingle relates to it height? Did you keep the base length the same? It is unclear what you mean by the angle was equal to the height. If you can clarify, I would be more than happy to figure out your question!

[candice]

Hey!

I think the relationship that I found was that the sine of an angle is equal to the height of a right angled triangle, if the hypotenuse of that triangle is 1cm in length. Therefore my slope heights were equal to the sine of the angle multiplied by 100 (my hypotenuse was 1m). Is this possible? and is there some mathematical rule that I can use to prove it in my discussion?
(I kept the hypotnuse length constant, but the change in angle caused the base length of the triangle to vary)

Thanx a lot Terik!

[deleted-2131]

Candice,

When you talk about slope length, do you mean the length of the hypotenuse, or the length of a altitude to the hypotenuse? It would help greatly if you were to send the degree and length measurements of a few of the sample triangles, I will work them out and figure out exactly what you are asking about. I will notify you of any relationships I find, and try to explain them to you.

Good Luck!

[shijun]

Candice,

The sine of an angle (let's call it angle A) is equal to the side of the triangle OPPOSITE to angle A divided by the hypotenuse (the longest side). Sine is simply a ratio (and we are only talking about right triangles). You can try to play around with different values of A e.g. 30 degrees, 45 degrees, 60 degrees, or even 90 degrees, though the resulting shape would no longer be a triangle with A = 90 degrees (can you see why?).

Anyway, the marshmallow example was to illustrate that the more straight (directly down) you drop an object (especially a round one), the smaller the "crater." Can you see why?

Shijun
Science Buddies Staff

[candice]

Dear Terik

The actual length of the hypotenuse is constant. (1cm)

For example - the sine of 15 degrees is o,25cm (2,5mm) and the sine of 30 degrees is 0,5cm (5mm).

[candice]

Dear Shijun

My experiment was done using a slope and rolling a ballbearing down that slope onto plasticene. Visualising this then, I had a right angled triangle and kept the 90 degree angle, and the 1m hypotenuse length constant. When I speak of changing angles, I am talking about the angle opposite the height.

My results were as follows: As the angle increased, the diameter, depth and volume of the crater increased.

I think this is so because as the angle increases, the speed of the ballbearing increases, and thus it hits the plasticene harder - making more of the ball submerge.

Is this a reasonable explanation? Could you explain this to me a little more scientifically please

thanx so much

[deleted-2131]

Candice,

Your inference about speed are correct. When the ball is placed at a steeper angle it gains more potential energy. Therefore it releases more kinetic energy when it strikes the plasticene, causing a larger crater.

[shijun]

Terik,

Thanks for clarifying this for candice! I am glad to see the discussion going well.

Candice,

Here is an even more scientific explanation (bear with me if it seems a bit too advanced for now, and you can always ask your parents or science/physics teacher about this):

-As your angle (opposite to height as you have said) increases, the height increases as well.
-Potential energy = mass * g * height, and g = about 9.806 (it's a constant)
-As the ball rolls down, the Potential energy gets transferred into kinetic (as the ball hits the ground, the height is 0, and all potential energy is transferred into kinetic)
-So we can say: mass * g * height = kinetic energy = 1/2 * m * v ^ 2 (that is, raised to the second power, or squared)
-As you can see as height increases, the potential energy increases, and the kinetic energy increases and the velocity, v (or speed if you care to simplify in this case) also increases
-So the ball travels faster! And we have shown this mathematically above!

Note that in this case, I have assumed no friction, which is non-realistic. And the discussion gets more complicated with friction (I need to bring in more equations), but for the present, this is the gist of it.

Hope this helps!

Shijun
Science Buddies Staff

[candice]

Thanx so much! That definately helps me!

I have to hand the project in very soon now, so I'm putting it all together -

So - For the calculation section I have put in what you told me, a calculation working out height and one for velocity - what other calculation do you think would be relevent?

For observations I simply said that I noticed that the crater increased in depth, volume and diameter, and I said that I noticed that the height was equal to the sine of the oppsite angle (as I have told you before). Is there anything else that I could have observed?

For discussion I have explained that the reason the height was equal to the sine of the opposite angle is because sine is equal to opposite over hypotenuse, and my hypotenuse was 1cm.
I also discussed that the crater sizes increased as the angle of the slope increased due to the increase of velocity of the ball and therefore more kinetic energy acted on the plasticene. Is there nothing more complex to do with the crater formation that I can discuss???

See, I expected the craters to form as you indicated with a marshmallow... and since they did not, I fear that my explanations are far too simple. Please help me again

Thank you for all your guidance so far

[shijun]

One other thing you'll need to be careful about is that technically, you can't say the height is equal to the sine of an angle. Sine is simply a ratio (no unit), while height has a unit. 1 can be 1 cm, or 1 m, or 1 km. you can say something like the height is equal to the sine of angle a in cm, or in m because I have assumed the hyp to be 1 cm.

Also, since we are dealing with a simplified case, you should say "I am using a smooth surface where I am assuming the effects of friction is negligible."

Shijun

[candice]

Please, I really dont know what else to discuss in my discussion!

Anyones help would be appreciated - My discussion is FAR too short and simple! I have to discuss the sciientific reasons behind what I observed... what else could I say???

I have searched the net, but I just find information on normal craters - and the craters I formed did not form as those do in nature.

HELP PLEASE!!!

[deleted-2131]

Candice,

In your discussion you should first describe what happened. Then tell the scientific reasons why what you observed occurred. The next part of a discussion is to review any problems you had. After that, it is best to discuss the applicability of your project (i.e. how close is it to what happens in the real world) If your experiment did not agree with what your research shows, say so! Discuss the limiting factors in your experiement. Then describe what questions were raised by your experiment, and explore some extensions of your project. If you have specific questions, I can help you. However, it is diffuicult to tell you exactly what yo put in your disscusion.

Good Luck

[candice]

Why are impact craters always circular?

Why is the rim crest highest on the side closest to the angle of incidence?

Why do the crater flanks extend to greater distances on the side closest to the angle of incidence?

[candice]

I just want to say thank you againto terik and shujin for all your help. I handed my project in today.

I really enjoyed doing this project, and I am still interestd to know the answers to those few questions if anyone knows. I learnt alot, and I enjoyed it so...

thanx again

[deleted-2131]

Candice,

It was my pleasure to help you. Thats what Science Buddies is all about! I will look up why impact craters are always round. As to the other questions, it all has to do with inertia. The more oblique that angle at which the impactor hits the surface, the more energy is sent in that direction. This causes the material to move more in the direction that the impactor is traveling. It is difficult to explain without a diagram. I will try to find some way to put a diagram in a message. If you have any other questions, just ask!

[candice]

So does that mean that the rim and crater flanks are actually highest on the side not facing the ramp?

I think I understand if this is the case

[deleted-2131]

Candice,

The rim height will be taller on the side of the crater closest to the ramp. Because the impactor is coming in at an angle, the inertia is coming in at an angle. Therefore more energy will be send forward (away from the ramp) than backward (towards the ramp.) Since the force is being applied at an angle, the particles the inertia acts on move in the direction of the force. (i.e. forward) So, the particles farthest from the ramp get displaced away from the ramp. To sum up, since the force is traveling forward, the particles move more forward, resulting in a greater net movement of particles, thereby decreasing the height of the rim. The side of the crater nearest the rim is not moved as much because less of the inertial force is traveling that way, so the particles do not move as much, causing them to bunch up and form the tall rim that you see. If this does not make sense, hold on a few more days, and I will have a sketch that you can look at.

[deleted-2131]

Candice,

The rim height will be taller on the side of the crater closest to the ramp. Because the impactor is coming in at an angle, the inertia is coming in at an angle. Therefore more energy will be send forward (away from the ramp) than backward (towards the ramp.) Since the force is being applied at an angle, the particles the inertia acts on move in the direction of the force. (i.e. forward) So, the particles farthest from the ramp get displaced away from the ramp. To sum up, since the force is traveling forward, the particles move more forward, resulting in a greater net movement of particles, thereby decreasing the height of the rim. The side of the crater nearest the rim is not moved as much because less of the inertial force is traveling that way, so the particles do not move as much, causing them to bunch up and form the tall rim that you see. If this does not make sense, hold on a few more days, and I will have a sketch that you can look at.