- #1
kingkong69
- 22
- 0
Hey there,
i) if it is traveling towards D as it passes through B
ii) if it is traveling away from D as it passes through B.
v^2=w^2(a^2-x^2) (v=velocity, w=angular speed, a=amplitude, x=stretched distance)
So, because A and E are the extreme points, with AE=60cm, therefore the a=30cm
Because period is 0.2s, 2*pi/T=angular velocity(w), so w=10pi=31.416
velocity at B: I used the SMH formula for velocity, v^2=w^2(a^2-x^2), x is the stretched distance, which is 0.15m from the center, so v^2=(10pi)^2*(0.3^2-0.15^2), v=8.162ms^-1
velocity at D: Same method applied, x=0.1m here. velocity at D=8.886ms^-1
From here on is just applied the distance formula with given distance, original velocity and final velocity. I think I messed up at this stage.
And finally deriving 0.029s, close but wrong![Devil :devil: :devil:](https://www.physicsforums.com/styles/physicsforums/xenforo/smilies/oldschool/devil.gif)
Thanks for the help
The Question
Points A,B,C,D, and E lie in a straight line. AB=BC=15 cm, CD=10 cm and DE=20 cm. A particle is moving with SHM so that A and E are the extreme positions of its motion. The period of the motion is 0.2s. Find the time the particle takes to get from B to D i) if it is traveling towards D as it passes through B
ii) if it is traveling away from D as it passes through B.
Formulas
w=2pi/T (w=angular speed, pi=3.14159, T=period)v^2=w^2(a^2-x^2) (v=velocity, w=angular speed, a=amplitude, x=stretched distance)
My attempt
First of all, the given answer is i) 0.0275s ii) 0.0942sSo, because A and E are the extreme points, with AE=60cm, therefore the a=30cm
Because period is 0.2s, 2*pi/T=angular velocity(w), so w=10pi=31.416
velocity at B: I used the SMH formula for velocity, v^2=w^2(a^2-x^2), x is the stretched distance, which is 0.15m from the center, so v^2=(10pi)^2*(0.3^2-0.15^2), v=8.162ms^-1
velocity at D: Same method applied, x=0.1m here. velocity at D=8.886ms^-1
From here on is just applied the distance formula with given distance, original velocity and final velocity. I think I messed up at this stage.
And finally deriving 0.029s, close but wrong
![Devil :devil: :devil:](https://www.physicsforums.com/styles/physicsforums/xenforo/smilies/oldschool/devil.gif)
Thanks for the help