Help with vectors

P

philomina

New member
Joined
Oct 31, 2010
Messages
7
Please help me in finding answer for the following as early as possible as my test on the same is in two days time. I am totally confused. :cry:

A particle P is moving with constant velocity (-5i+8j) m/s. Find
a) the speed of P
b) the direction of motion of P, giving your answer as a bearing

At time t=0, P is at the point with position vector (7i-10j) m relative to a fixed origin O. When t=3 s, the velocity of P changes and it moves with velocity (ui+vj) m/s, where u and v are constants. After a further 4 s, it passes through O and continues to move with velocity (ui+vj) m/s.

c) Find the values of u and v.
d) Find the total time taken for P to move from A to a position which is due south of A.
 
philomina said:
Please help me in finding answer for the following as early as possible as my test on the same is in two days time. I am totally confused. :cry:

A particle P is moving with constant velocity (-5i+8j) m/s. Find
a) the speed of P
b) the direction of motion of P, giving your answer as a bearing

At time t=0, P is at the point with position vector (7i-10j) m relative to a fixed origin O. When t=3 s, the velocity of P changes and it moves with velocity (ui+vj) m/s, where u and v are constants. After a further 4 s, it passes through O and continues to move with velocity (ui+vj) m/s.

c) Find the values of u and v.
d) Find the total time taken for P to move from A to a position which is due south of A.
Click to expand...

1) a) speed is the magnitude of the velocity.

2) Constant velocity indicates linear motion.

Please share your work with us, indicating exactly where you are stuck - so that we may know where to begin to help you
 
Subhotosh Khan said:
philomina said:
Please help me in finding answer for the following as early as possible as my test on the same is in two days time. I am totally confused. :cry:

A particle P is moving with constant velocity (-5i+8j) m/s. Find
a) the speed of P
b) the direction of motion of P, giving your answer as a bearing

At time t=0, P is at the point with position vector (7i-10j) m relative to a fixed origin O. When t=3 s, the velocity of P changes and it moves with velocity (ui+vj) m/s, where u and v are constants. After a further 4 s, it passes through O and continues to move with velocity (ui+vj) m/s.

c) Find the values of u and v.
d) Find the total time taken for P to move from A to a position which is due south of A.
Click to expand...

1) a) speed is the magnitude of the velocity.

2) Constant velocity indicates linear motion.

Please share your work with us, indicating exactly where you are stuck - so that we may know where to begin to help you
Click to expand...



Hi, I was able to work out parts a, b and c in the following manner. However, I didn't understand how to approach part d of the question. Any help would be very much appreciated.
a) speed was 9.43m/s (3 s.f)

b) Bearing was 360 - arctan5 5/8 = 328

c) At t=3, position vector of P = (7-15)i + (-10+24)j= -8i + 14j
Hence -8i +14j +4(ui + vj) = 0
Therefore, u = 2, v = -3.5

Thanks.
 
philomina said:
Subhotosh Khan said:
philomina said:
Please help me in finding answer for the following as early as possible as my test on the same is in two days time. I am totally confused. :cry:

A particle P is moving with constant velocity (-5i+8j) m/s. Find
a) the speed of P
b) the direction of motion of P, giving your answer as a bearing

At time t=0, P is at the point with position vector (7i-10j) m relative to a fixed origin O. When t=3 s, the velocity of P changes and it moves with velocity (ui+vj) m/s, where u and v are constants. After a further 4 s, it passes through O and continues to move with velocity (ui+vj) m/s.

c) Find the values of u and v.
d) Find the total time taken for P to move from A to a position which is due south of A.
Click to expand...


Thanks.
Click to expand...
Click to expand...

Where is A ?
 
Where is A ?
Click to expand...

I am sorry I missed out the point A. The second part of the question is:

At time t=0, P is at the point A with position vector (7i-10j) m relative to a fixed origin O. When t=3 s, the velocity of P changes and it moves with velocity (ui+vj) m/s, where u and v are constants. After a further 4 s, it passes through O and continues to move with velocity (ui+vj) m/s.

c) Find the values of u and v.
d) Find the total time taken for P to move from A to a position which is due south of A.
 
You must log in or register to reply here.
Top