Vector Scalar Product and KE questions

AI Thread Summary
The discussion focuses on understanding scalar multiplication of vectors and finding angles between them, particularly using the formula cos(theta) = (a * b)/(|a||b|) for the dot product. The user initially struggled with questions from a physics set after missing a class on these topics. They successfully solved the first question using the kinetic energy formula k = 0.5 * m * v^2 but were unclear about the second question. Ultimately, the user reported that they figured out all the problems with assistance from others. The exchange highlights the importance of peer support in grasping complex physics concepts.
Walczyk
Messages
4
Reaction score
0
Just a few questions from this set I have to do, I missed the class on these topics so I'm just a little confused with these last few problems.

http://img161.imageshack.us/img161/2307/problem43eu.png

Concerning sets 38-39, and 40-41, I've grasped how to scalar multiply these vectors, but not how to find the angle it seems, wondering if anybody can check those out. as for the last set, i was able to find the first answer with k=.5*m*v^2, but I'm not sure what the second question is asking. I missed the class on these topics (accelerated physics in the summer, awfully bad to miss a class). thanks in advance!
 
Last edited by a moderator:
Physics news on Phys.org
I believe the formula you need to use is something like:

cos(theta) = (a * b)/(|a||b|)

Where * is the dot product of a and b.
 
aye, i wroked those angles out, inverse cosine.
edit: I've figured out all the problems, thanks for the help everyone.
 
Last edited:

Thread 'Errors and significant figures'

I multiplied the values first without the error limit. Got 19.38. rounded it off to 2 significant figures since the given data has 2 significant figures. So = 19. For error I used the above formula. It comes out about 1.48. Now my question is. Should I write the answer as 19±1.5 (rounding 1.48 to 2 significant figures) OR should I write it as 19±1. So in short, should the error have same number of significant figures as the mean value or should it have the same number of decimal places as...
View full post »
Thread 'A cylinder connected to a hanging mass'

Thread 'A cylinder connected to a hanging mass'

Let's declare that for the cylinder, mass = M = 10 kg Radius = R = 4 m For the wall and the floor, Friction coeff = ##\mu## = 0.5 For the hanging mass, mass = m = 11 kg First, we divide the force according to their respective plane (x and y thing, correct me if I'm wrong) and according to which, cylinder or the hanging mass, they're working on. Force on the hanging mass $$mg - T = ma$$ Force(Cylinder) on y $$N_f + f_w - Mg = 0$$ Force(Cylinder) on x $$T + f_f - N_w = Ma$$ There's also...
View full post »

Similar threads

Generalized coordinates- scalar product
Replies
1
Views
1K
Finding the Scalar Triple Product of Three Vectors
Replies
2
Views
1K
How Does Tangential Velocity Relate to Vector Products in Rotational Motion?
Replies
6
Views
2K
Stuck on a few Vector homework problems
Replies
1
Views
2K
Evaluating scalar products of two functions
Replies
1
Views
1K
I The Road to Reality - exercise on scalar product
Replies
36
Views
4K
Question on Calculating Coulomb force in VECTOR FORM
Replies
3
Views
3K
I Angle between vectors via scalar product vs vector product
Replies
3
Views
2K
I Dot product of two vector operators in unusual coordinates
Replies
14
Views
2K
B Minkowski metric, scalar product, why the minus sign?
Replies
14
Views
5K

Hot Threads

Recent Insights

Back
Top