All Mechanics DOUBTS HERE!!!

[The Golden Girl =D]

Guys I've got an exam tomorrow so can you please answer this Question for me

Hmm in this Equation :

S=ut+0.5a(time Square)

When do we take the S as Displacement and when do we take it as Distance

Please help

thx =]

[iluvme]

S is always the displacement and never the distance.

[The Golden Girl =D]

S is always the displacement and never the distance.

Hmm well here is a Question that says :

a book falls off the top of a bookcase.the shelf is 1.4m above the a wooden floor . (a) find the time the book takes to reach the floor , (b) the speed with which the book strikes the floor .

here we used the 1.4m as distance in the Equation I mentioned Prior , while in another Question :

A ball is projected vertically upwards ,from a point X which is 7m above the ground , with speed 21 m/s .Find (a) the greatest height above the ground reached by the ball , (b) the time of flight of the ball

here we used displcement as -7 , hence in the Equation S was used as Discplacement .

y there as distance and here as dicplacement 

[The Golden Girl =D]

Hmm well here is a Question that says :

a book falls off the top of a bookcase.the shelf is 1.4m above the a wooden floor . (a) find the time the book takes to reach the floor , (b) the speed with which the book strikes the floor .

here we used the 1.4m as distance in the Equation I mentioned Prior , while in another Question :

A ball is projected vertically upwards ,from a point X which is 7m above the ground , with speed 21 m/s .Find (a) the greatest height above the ground reached by the ball , (b) the time of flight of the ball

here we used displcement as -7 , hence in the Equation S was used as Discplacement .

y there as distance and here as dicplacement 

I'll go study since I still got some stuff to go over , So I'll see this thread in the morning iA =]

Please DO Help , I really need this 

thx =D

[iluvme]

PM

[The Golden Girl =D]

reading it =]

[elemis]

For the first question there is an acceleration involved therefore we use the equations of motion.

However, the second question states the object falls with constant velocity indicating no acceleration hence we can use the simple equation :

speed = distance/time

[astarmathsandphysics]

cant answer this until my pc is fixed. Sorry

[@d!_†oX!©]

Hey guys!

I have an exam in 3 days from now, and I feel so dumb cuz I don't know one whole chapter
Thought the sf people would be my last bet, so here it goes.
The problem is "Centre of Mass". Basically, the whole topic is a problem, but I guess posting all the questions that I have will be too much
So, I would like if someone could explain my the basic concept behind it, using the following two types of questions I have.

[astarmathsandphysics]

here

[@d!_†oX!©]

here

Thanks astar! You're always the rescue sir 

[@d!_†oX!©]

Another one:

Thanks in advance

[astarmathsandphysics]

here

[The Golden Girl =D]

M1 Edexcel book page 101 No.4 .

A particle of mass 6 kg hangs in eguilibrium , suspended by two light extensible strings ,inclined at 60 degree and 45 degree to the horizontal ,as shown. Find the tension in each of the strings.

Answer is : S = 30.4 or 30.5 and T = 43.0 ...

what the hell is S o.0 ?

[astarmathsandphysics]

here