Dynamics problem


by grothem
Tags: dynamics
grothem
grothem is offline
#1
Feb20-08, 01:35 AM
P: 23
In an electricity experiment, a 1.10 g plastic ball is suspended on a 59.0 cm long string and given an electric charge. A charged rod brought near the ball exerts a horizontal electrical force F on it, causing the ball to swing out to a 19 degree angle and remain there.



What is the magnitude of F?
What is the tension in the string?




Ok, I set up my free body diagram and set the forces along the y-axis = 0.
I came up the the equation, .1078cos(19) + F -mg=0 , which does not give me the right magnitude for F, what is wrong with my equation? The length of the string is only needed for the tension part of problem correct? But I do not know how to set that up either.
Phys.Org News Partner Science news on Phys.org
Better thermal-imaging lens from waste sulfur
Hackathon team's GoogolPlex gives Siri extra powers
Bright points in Sun's atmosphere mark patterns deep in its interior
lavalamp
lavalamp is offline
#2
Feb20-08, 02:21 AM
lavalamp's Avatar
P: 280
Well vertically you have:
mg = Tcos19

And horizontally:
F = Tsin19

So I'd find the tension first, then use that to find the electrostatic force on the ball.
dr_d_is_cool
dr_d_is_cool is offline
#3
Feb20-08, 02:26 AM
P: 9
this isnt really what id call my good point in physics but i would say that you mite need to use the length of the string for more then just the tension.. set up ur thingo with various lengths of cord and check the differences.... this probably didnt help u much but as i said,,, not my good point

grothem
grothem is offline
#4
Feb20-08, 08:47 AM
P: 23

Dynamics problem


Ok so I came up with T=.0114 and F=.0037N, which is correct. Thank you!


Register to reply

Related Discussions
Dynamics Problem Introductory Physics Homework 10
Dynamics Problem Engineering, Comp Sci, & Technology Homework 1
Dynamics Problem...help plz! Introductory Physics Homework 3
Dynamics Problem Introductory Physics Homework 8
Dynamics problem. Introductory Physics Homework 2