• Support PF! Buy your school textbooks, materials and every day products Here!

I need to find the velocity vector two results ! help please

  • #1

Homework Statement



find the velocity vector for the time t=2s

i have given r(t)=
(50*sin((1/2)*t)*cos ((1/4)t),
-50*sin((1/2)*t)*sin((1/4)t))

Homework Equations



i also know that r(t)=
(50*sin(k*t)*cos (1/2k*t),
-50*sin(k*t)*sin(1/2k*t))
where k = 0,5s-1

The Attempt at a Solution


so i tried solving it and my attempt is shown in the attachment where i got the result
v(2)=6,8;-15,7

but someone said it has to be solved with the following results
25m/s*[0,272449, -0,62826] so im quite confused now..

so i dont know what to do and HOPE VERY MUCH someone will check my result v(2)=6,8;-15,7 and tell me if its right or not and if so what i can do to get the right result
 

Attachments

Answers and Replies

  • #2
326
3
so i tried solving it and my attempt is shown in the attachment where i got the result
v(2)=6,8;-15,7

but someone said it has to be solved with the following results
25m/s*[0,272449, -0,62826] so im quite confused now..

so i dont know what to do and HOPE VERY MUCH someone will check my result v(2)=6,8;-15,7 and tell me if its right or not and if so what i can do to get the right result
Actually, your answer is correct if you refer angles with radians only. There seems to be no incorrect approach here.

What someone just did is to factor out 25 for each vector. Then, simplify the values. Yours and someone's answers are equivalent.

Nicely done!
 
  • #3
Actually, your answer is correct if you refer angles with radians only. There seems to be no incorrect approach here.

What someone just did is to factor out 25 for each vector. Then, simplify the values. Yours and someone's answers are equivalent.

Nicely done!
Oh GREAT !! this answer is the one that has made me most happy ever <3

:)
 

Related Threads on I need to find the velocity vector two results ! help please

  • Last Post
Replies
5
Views
1K
  • Last Post
Replies
1
Views
2K
  • Last Post
Replies
1
Views
891
Replies
1
Views
7K
Replies
9
Views
2K
Replies
3
Views
8K
  • Last Post
Replies
1
Views
10K
  • Last Post
Replies
1
Views
9K
Replies
3
Views
833
Top