Math Is Fun Forum

Au101

Member

Registered: 2010-12-01

Posts: 353

Dynamics

Hi guys, I have a mechanics question on what I think is dynamics.

A particle P of mass 2 kg is acted on by two forces

And

(a) Show that the acceleration of P is

Which we do with

At time t = 0 P is at the point with position vector

Relative to a fixed origin O and has velocity

Calculate at time t = 3 seconds

(b) The velocity of P

Which is:

(c) The position vector of P

Here is where I am stuck. Does anybody have any suggestions? Thanks.

Last edited by Au101 (2011-03-18 14:22:27)

sameer mishra

Member

Registered: 2010-08-27

Posts: 64

Re: Dynamics

Fnet=(6i+2j)
anet={Fnet/2}=(3i+j)........Ans
Vx=V(initial)+ax*t
     4+3*3=13
Vy=0+3*1=3
Vnet=Vxi+Vyj
      (13i+3j).........Ans
X=X0+v(initial)*t+1/2*ax*t^2
  =2+4*3+1/2*3*9
  =27.5
Y=Y0+0+1/2*1*9
=-1+4.5
=3.5
="hence requried position vector=(27.5i+3.5j)".........Ans

Au101

Member

Registered: 2010-12-01

Posts: 353

Re: Dynamics

Aha, got it. Thanks Sameer