An object travels along a curved path. Given acceleration and angle, find velocity.


by shiv604
Tags: curved path., multiple choice, physics
shiv604
shiv604 is offline
#1
Sep16-12, 07:03 PM
P: 6
1. The problem statement, all variables and given/known data

An object is travelling along a curved path. At a particular instant the angle between its velocity vector and its acceleration vector is 128 degrees. The magnitude of its acceleration vector is 6.68 m/s2.

At that instant, what is the particle's rate of change of speed? (in m/s2)

Pick one:

a. 6.68
b. -6.68
c. -4.11
d. 4.11
e. -5.26
f. 5.26

2. Relevant equations

I am not sure which equation to use. That is where I am stuck. No equation I can think of helps me.


3. The attempt at a solution

Created a triangle, one side is the acceleration, the other is velocity. They are bound by a 128 angle. Not sure how to carry on from this point; help needed.
Phys.Org News Partner Science news on Phys.org
SensaBubble: It's a bubble, but not as we know it (w/ video)
The hemihelix: Scientists discover a new shape using rubber bands (w/ video)
Microbes provide insights into evolution of human language
Simon Bridge
Simon Bridge is offline
#2
Sep16-12, 08:55 PM
Homework
Sci Advisor
HW Helper
Thanks ∞
PF Gold
Simon Bridge's Avatar
P: 11,095
Don't worry about the equation - sketch the diagram.
Draw the two vectors.
Label the angle.
Continue the velocity with a dotted line.
resolve the acceleration against the velocity.

It's just trigonometry - but you have a bit of physics to do first.

The perpendicular component of the acceleration changes the .... what?
The parallel component changes the ...?
shiv604
shiv604 is offline
#3
Sep16-12, 09:51 PM
P: 6
Hmm. Well I made a triangle, one side velocity, the other acceleration; which was bound by 128 degrees.
I'm stuck on what to do next with this triangle.
I have never seen a problem like this before. I have tried my class notes, my textbook, and google. I cannot seem to grasp what the question is getting at. :(

Simon Bridge
Simon Bridge is offline
#4
Sep16-12, 10:02 PM
Homework
Sci Advisor
HW Helper
Thanks ∞
PF Gold
Simon Bridge's Avatar
P: 11,095

An object travels along a curved path. Given acceleration and angle, find velocity.


How to describe it ... put the x axis along the velocity vector and get the x and y components of the acceleration.

The component along the y axis changes the direction of the velocity.
(Like in "circular motion".)

The component along the x axis changes the magnitude, the speed.
(Like in "kinematics".)
shiv604
shiv604 is offline
#5
Sep17-12, 04:34 PM
P: 6
ok that makes sense!
I got 4.11 for x, and 5.26 for y.
I am confused on which one affects the rate of change.
Also once I do find which component affects the rate of change, would it be positive or negative?
shiv604
shiv604 is offline
#6
Sep17-12, 06:13 PM
P: 6
ooooh 4.11
shiv604
shiv604 is offline
#7
Sep17-12, 06:14 PM
P: 6
thanks a bunch!
Simon Bridge
Simon Bridge is offline
#8
Sep17-12, 06:14 PM
Homework
Sci Advisor
HW Helper
Thanks ∞
PF Gold
Simon Bridge's Avatar
P: 11,095
Don't forget the units.

You now have two acceleration vectors - draw the arrows on your diagram.

You just need to realize that acceleration points in the same direction as force.
So the direction of the acceleration tells you the direction of the force.
You should be able to figure out which is which from that.

If the force would slow it down, then the change in velocity is negative.
If the force would speed it up, then the change in velocity is positive.
shiv604
shiv604 is offline
#9
Sep17-12, 06:17 PM
P: 6
yes thank you simon!
Simon Bridge
Simon Bridge is offline
#10
Sep17-12, 06:49 PM
Homework
Sci Advisor
HW Helper
Thanks ∞
PF Gold
Simon Bridge's Avatar
P: 11,095
No worries: now you have a fancy new tool :)


Register to reply

Related Discussions
Find the magnitude of acceleration along a curved path Introductory Physics Homework 0
find initial velocity given angle and distance to go over an object Introductory Physics Homework 15
Find initial Velocity with only distance, angle, and acceleration. Introductory Physics Homework 5
Motion and force along a curved path-angle of curves? Introductory Physics Homework 1
An object travels in a straight line at a uniform velocity Introductory Physics Homework 3