Qualification > Math
All Mechanics DOUBTS HERE!!!
WARRIOR:
--- Quote from: astarmathsandphysics on March 02, 2012, 10:59:49 am ---BOOK is correct!!!
When I did it the first time I ignored the 12i
and the second time I got 12i+6j=18j
--- End quote ---
HOW :o im so slow , i still dont understand how 12i= 3i + ( 4 -10 ) j could be 12i+6j=18j
astarmathsandphysics:
i and j are not like terms so 12i+6j is not equal to 18j
Shall I make a video the this?
theeducationchannel.info
WARRIOR:
At time t seconds , a particle P has position vector r with respect to a fixed origin O , where
r= [ (3t(sq) - 4) i + ( 8 - 4t(sq) ) j ]
a Show that the acceleration of P is a constant .
b Find the magnitude of the acceleration of P and the size of the angle which the acceleration makes with j .
I get magnitude of acceleration = 10
But size of angle is 143.1 HOWWWWWWWWWWWWWWW
astarmathsandphysics:
Differentiate twice get a=6i-8j
This is at an angle tan^(-1) (8/6)=53.13 below the x axis (plot (6,-8))
add 90 cos it is the angle with the j axis
LekhB:
Thanks for the previous answers. Now, I got stuck with 3 different questions while I was doing my homework.
1/. A car is moving along a straight road with uniform acceleration. The car passes a check-point A with a speed of 12 m/s and another check-point C with a speed of 32 m/s. The distance between A and C is 1100m.
(i) Find the time, in s, taken by the car to move from A to C.
(ii) Given that B is the mid-point of AC, find in m/s to 1 decimal place, the speed with which the car passes B.
2. A, B and C are 3 points on a straight line, in that order, and the distance AB and AC are 45m and 77m respectively. A particle moves along the straight line with constant acceleration 2 m/s². Given that it taked 5 seconds to travel from A to B, find the time taken to travel from A to C.
3. An aircraft accelerates along the runway with constant acceleration a m/s². 3 points on the runway are A, B, C, where the distances AB and AC are each 120m. The speed of the aircraft as it passes A is u m/s. The aircraft takes 6s to cover the distance AB and 4s to cover the distance BC. Find the values of a and u.
It would be awesome if anyone could help. Cheers.
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