# Anyone a Master of Physics?

Ramned
Posers and Puzzles 18 Sep '07 19:56
1. Ramned
The Rams
18 Sep '07 19:562 edits
I am going to ask a set of 30 conceptual questions. They will get harder and harder. If anyone can get all 30, they are a true MASTER! Some of these questions are true stumpers.

Let's kick it off with the basics: Dimensional Analysis.

#1. The height of a horse is sometimes given in the units of "hands." Why is this a poor standard of length?
2. wolfgang59
Mr. Wolf
18 Sep '07 20:47
Originally posted by Ramned
I am going to ask a set of 30 conceptual questions. They will get harder and harder. If anyone can get all 30, they are a true MASTER! Some of these questions are true stumpers.

Let's kick it off with the basics: Dimensional Analysis.

[b]#1. The height of a horse is sometimes given in the units of "hands." Why is this a poor standard of length?
[/b]
Sometimes? In UK a horse's height is measured in hands.

1 hand = 4 inches.

The inch being defined as 1/12 of a yard.

The yard being defined as EXACTLY 0.9144 metres (since 1956)

I cannot see any problem! (And why physics?)

PS Cant wait for next 29 ..................
3. Ramned
The Rams
18 Sep '07 20:551 edit
Originally posted by wolfgang59
Sometimes? In UK a horse's height is measured in hands.

1 hand = 4 inches.

The inch being defined as 1/12 of a yard.

The yard being defined as EXACTLY 0.9144 metres (since 1956)

I cannot see any problem! (And why physics?)

PS Cant wait for next 29 ..................
:'(

No...I'll explain if people continue to miss this, which I really plead won't happen. You're thinking way too deep. This is only a fundamental of physics: the idea of precision.

Next guess?
4. wolfgang59
Mr. Wolf
18 Sep '07 21:09
Originally posted by Ramned
:'(

No...I'll explain if people continue to miss this, which I really plead won't happen. You're thinking way too deep. This is only a fundamental of physics: the idea of precision.

Next guess?
1. I am not a deep thinker! ðŸ™„

2. What IS the question? ðŸ˜•

3. It was NOT a guess! ðŸ˜
5. 18 Sep '07 21:12
Originally posted by Ramned
I am going to ask a set of 30 conceptual questions. They will get harder and harder. If anyone can get all 30, they are a true MASTER! Some of these questions are true stumpers.

Let's kick it off with the basics: Dimensional Analysis.

[b]#1. The height of a horse is sometimes given in the units of "hands." Why is this a poor standard of length?
[/b]
Dimensionally speaking the standard unit for length is the meter, so perhaps Ramned is meaning that the "hand" is based in imperial units (4 inches), so it is awkward to use in standard (SI) units. However, this is not really a fundamental problem.

I suspect that the reason "hands" are not a very appropiate unit of measure is to do with the resolution of the hand system. Usually the height of a horse is measured to the nearest whole hand (i think?), which means it could be as inacurate as +/- 2 inchs. This is a fundamental problem with the resolution of the hand scale and will be a source of a significant error if precise height measurements are required.
6. Ramned
The Rams
18 Sep '07 23:54
Originally posted by MattP
Dimensionally speaking the standard unit for length is the meter, so perhaps Ramned is meaning that the "hand" is based in imperial units (4 inches), so it is awkward to use in standard (SI) units. However, this is not really a fundamental problem.

I suspect that the reason "hands" are not a very appropiate unit of measure is to do with the resolution of th ...[text shortened]... ale and will be a source of a significant error if precise height measurements are required.
You are correct. Hands vary in size = not precise as, say, a meter. The length of a hand varies from person to person, so it isn't a useful standard of length.

QUESTION 2 FOLLOWS.
7. Ramned
The Rams
18 Sep '07 23:55
Motion (One dimension)

2. If a car is traveling eastward, can its acceleration be westward? Explain.
8. 19 Sep '07 02:31
Originally posted by Ramned
Motion (One dimension)

[b]2. If a car is traveling eastward, can its acceleration be westward? Explain.
[/b]
Yes... slowing down gives an acceleration backwards which of course is westward.
9. coquette
19 Sep '07 04:13
next, #3?
10. Ramned
The Rams
19 Sep '07 11:46
Originally posted by XZantoth
Yes... slowing down gives an acceleration backwards which of course is westward.
Yes.
11. Ramned
The Rams
19 Sep '07 11:513 edits
A harder one on motion...this is still basic though.

Two Dimensional Motion

3. A wrench is dropped from the top of a 10-m mast on a sailing ship while the ship is traveling in a straight line at 20 knots. Where will the wrench hit the deck?
12. 19 Sep '07 11:54
Assuming no wind, at the bottom of the mast.
13. 19 Sep '07 11:55
Originally posted by Ramned
A harder one on motion...this is still basic though.

Two Dimensional Motion

[b]3. A wrench is dropped from the top of a 10-m mast on a sailing ship while the ship is traveling in a straight line at 20 knots. Where will the wrench hit the deck?
[/b]
Near the bottom of the mast. Because at the beginning of the motion it already has a speed of 20 knots in the horizontal direction.
14. Ramned
The Rams
19 Sep '07 11:56
Originally posted by kbaumen
Near the bottom of the mast. Because at the beginning of the motion it already has a speed of 20 knots in the horizontal direction.
Perfect.
Next question to follow....
15. Ramned
The Rams
19 Sep '07 12:001 edit
Motion continuing...hope they're not too hard for ya yet ðŸ˜‰

Laws of Motion

4. A large crate is placed on the bed of a truck. (A) As the truck accelerates forward, the crate remains at rest relative to it...what force causes the crate to accelerate forward? (B) If the driver slams on the brakes, what could happen to it?