Simple Harmonic Motion: Determine Velocity at t=0.250s

[Moe*]

_{}b]1. Homework Statement [/b)

The position of a 39.8 g oscillating mass is given by the equation x(t)= (2.00cm)cos(5t- 4.00$$\pi$$) where t is in seconds. Determine Velocity at t= 0.250s

M= 39.8 g
T= 1.2575 rad/s
K= 9.95e-1 N/m
initial postion= 2 cm

Homework Equations

V$$_{x}$$= -$$\omega$$Asin($$\omega$$t + $$\phi$$)

The Attempt at a Solution

the attempt i just substitued
V$$_{x}$$= -5 rad/s*2sin( 5.00(0.250)-4$$\pi$$)... but this didn't work and i don't understand why?

 

[Moe*]

for the the equations posted its supposed to be V subscript x= wAsin(wt + phi) and x(t) = (2.00cm)cos(5t - 4pi)

 

[Shooting Star]

The position of a 39.8 g oscillating mass is given by the equation x(t)= (2.00cm)cos(5t- 4.00$$\pi$$) where t is in seconds. Determine Velocity at t= 0.250s

What is the basic relation connecting velocity and position of any particle? Use that.

 

[mysqlpress]

_{}b]1. Homework Statement [/b)

The position of a 39.8 g oscillating mass is given by the equation x(t)= (2.00cm)cos(5t- 4.00$$\pi$$) where t is in seconds. Determine Velocity at t= 0.250s

M= 39.8 g
T= 1.2575 rad/s
K= 9.95e-1 N/m
initial postion= 2 cm

Homework Equations

V$$_{x}$$= -$$\omega$$Asin($$\omega$$t + $$\phi$$)

The Attempt at a Solution

the attempt i just substitued
V$$_{x}$$= -5 rad/s*2sin( 5.00(0.250)-4$$\pi$$)... but this didn't work and i don't understand why?

it seems work to me...

 

[Moe*]

Your right it does work, i guess I entered in the wrong units when i answered the question( m/s instead of cm/s).