# relative motion of two moving objects

• Apr 1st 2010, 10:23 PM
manik
relative motion of two moving objects
I need the ans with relevant figure :

Problem ::
Two particles P and Q, are 30m apart with Q due north of P. Particle Q is moving at 5m/s in a direction 90 deg and P is moving at 7m/s in a direction 30 deg. Find

(a) the magnitude and direction of the velocity Of Q relative to P,
(b) the time taken for Q to be due east of P,to the nearest second.
• Apr 2nd 2010, 12:59 AM
Hello manik
Quote:

Originally Posted by manik
I need the ans with relevant figure :

Problem ::
Two particles P and Q, are 30m apart with Q due north of P. Particle Q is moving at 5m/s in a direction 90 deg and P is moving at 7m/s in a direction 30 deg. Find

(a) the magnitude and direction of the velocity Of Q relative to P,
(b) the time taken for Q to be due east of P,to the nearest second.

Here's the diagram showing the velocities.

Use the Cosine Rule to find the magnitude of the velocity of Q relative to P.

Then find the component of this velocity in a North-South direction (indicated by the dotted line on the diagram).

From this you can work out the direction of this velocity, and how long it takes before Q is East of P.

Can you complete it now?