OH MY GOD projectiles
i hate projectiles
never know what to do!!!!
OCR Physics A  G481 Mechanics  [13/01/09][@1400]


(Original post by neomilan)
OH MY GOD projectiles
i hate projectiles
never know what to do!!!! 
(Original post by annaroberts20)
That carriage question sucked big time!!! Usually you would use the simple equation when they want average speed or average velocity or when the velocity is constant whereas u would use SUVAT when there is constant acceleration so changing velocity and on projectiles remember you only SUVAT on the vertical bit and then the simple equation on the horizontal bit 
Ah i see what happened just now, the two threads were merged!
Anyway, back to physics:
can someone explain how the measuring G experiment works... light gates thingy?
Thanks 
What I think it is, is its a metal ball held with a clamp thing above a light gate and another catcher thing at the bottom (sorry for these casual words )
When the ball is released the time starts and the speed is calculated as it passes the light gate, once it hits the ground, the timer is stopped 
(Original post by neomilan)
Ah i see what happened just now, the two threads were merged!
Anyway, back to physics:
can someone explain how the measuring G experiment works... light gates thingy?
Thanks
The light gate will measure how long it was broken for, so using speed = distance divided by time you can work out the speed through each light gate.
Then applying this to v^2 = u^2 + 2as, you can work out the acceleration, where U = speed at first light gate, and V = speed at second light gate.
Cos it's in free fall, a = g 
(Original post by beesbees)
Basically you have a card of a length. (say, 5cm). Then you have two light gates at a set distance apart (eg, 1m). You then have the first light gate above the other, and drop the card through them.
The light gate will measure how long it was broken for, so using speed = distance divided by time you can work out the speed through each light gate.
Then applying this to v^2 = u^2 + 2as, you can work out the acceleration, where U = speed at first light gate, and V = speed at second light gate.
Cos it's in free fall, a = g
And putting the numbers you will be left weith half of gravity times t squared. 
Can someone clarify this for me please??
I know that if you ignore air resistance, during free fall, the mass of an object does not affect the acceleration as the acceleration would always be equal to gravity.
But if you have horizontal acceleration like with a car, does the mass affect th acceleration? Cause if you look at F=ma and if you have the same force with a small mass, you have a bigger acceleration and vice versa.
Have I got this theory right? 
(Original post by annaroberts20)
Can someone clarify this for me please??
I know that if you ignore air resistance, during free fall, the mass of an object does not affect the acceleration as the acceleration would always be equal to gravity.
But if you have horizontal acceleration like with a car, does the mass affect th acceleration? Cause if you look at F=ma and if you have the same force with a small mass, you have a bigger acceleration and vice versa.
Have I got this theory right?
larger mass = smaller accelleration
at constant force 
(Original post by neomilan)
small mass = larger acceleration
larger mass = smaller accelleration
at constant force 
(Original post by annaroberts20)
But am I right that it doesn't apply to acceleration of free fall?
if there is another force acting on it, such as air resistance then it will be different
with that car you mentioned, i believe that since the car has a force (engine force) then its acceleration will change ... whereas a ball just allowed to free fall does not have forces added to it so its accelereation will be the same as G 
(Original post by neomilan)
Ah i see what happened just now, the two threads were merged!
Anyway, back to physics:
can someone explain how the measuring G experiment works... light gates thingy?
Thanks 
(Original post by Gav)
Make sure you write acceleration due to gravity as g not G  G is the gravitational constant.
erm, seeing as you're a physics degree student, can you verifiy if what i said is correct in terms of annaroberts's question
(Original post by neomilan)
(Original post by annaroberts20)
But am I right that it doesn't apply to acceleration of free fall?
if there is another force acting on it, such as air resistance then it will be different
with that car you mentioned, i believe that since the car has a force (engine force) then its acceleration will change ... whereas a ball just allowed to free fall does not have forces added to it so its accelereation will be the same as G 
According to the spcimen data sheet for 2008 Physics A
it says:
"The information in this sheet is for the use of candidates following
GCE Physics A H158 and H558.
Clean copies of this booklet must be available in the examination room, and must
be given up to the invigilator at the end of the examination.
Copies of this sheet may be used for teaching"
These forumlas will be given in the exam!
F cos (theta)
F Sin (theta)
a= delta V/ delta T
the 4 suvat equations
F=ma
moment = fx
Torque = fd
press. = F/A
Dens. = M/V
K.E = 1/2 mv^2
P.E = mgh
efficiency
stress
strain
and young modulus 
(Original post by Spongebob*No*Pants)
According to the spcimen data sheet for 2008 Physics A
it says:
"The information in this sheet is for the use of candidates following
GCE Physics A H158 and H558.
Clean copies of this booklet must be available in the examination room, and must
be given up to the invigilator at the end of the examination.
Copies of this sheet may be used for teaching"
These forumlas will be given in the exam!
F cos (theta)
F Sin (theta)
a= delta V/ delta T
the 4 suvat equations
F=ma
moment = fx
Torque = fd
press. = F/A
Dens. = M/V
K.E = 1/2 mv^2
P.E = mgh
efficiency
stress
strain
and young modulus
They may as Well give you the Mark Scheme as well. 
(Original post by Spongebob*No*Pants)
According to the spcimen data sheet for 2008 Physics A
it says:
"The information in this sheet is for the use of candidates following
GCE Physics A H158 and H558.
Clean copies of this booklet must be available in the examination room, and must
be given up to the invigilator at the end of the examination.
Copies of this sheet may be used for teaching"
These forumlas will be given in the exam!
That is indeed pretty much giving you about 50% on the paper already, because I am 100% sure you get 1 mark for writing an equation down, so it makes it a little easy doesn't it??
I spent AGES revising and memorising these equations and they just go ahead and give it to us!?!?!? 
(Original post by dave2k)
Haha, wtf??
That is indeed pretty much giving you about 50% on the paper already, because I am 100% sure you get 1 mark for writing an equation down, so it makes it a little easy doesn't it??
I spent AGES revising and memorising these equations and they just go ahead and give it to us!?!?!?
I HAD TO AND HAVE LEARNED ALL THE EQUATONS, and the ones for A2 as well.
and the New Spec comes along, and give you the formulas, they must think that you are REALLY stupid. 
Hehe, this has given me some hope that the paper will be simple!!
"What is the equation for pressure? (Please refer to your booklet for answer)" 
(Original post by dave2k)
Hehe, this has given me some hope that the paper will be simple!!
"What is the equation for pressure? (Please refer to your booklet for answer)"
Or THEY WILL RAPE YOU, with DIGUSTINGLY Hard questions. 
Whaat? That's just ridiculous!
They're not exactly hard to remember for this paper, anyway, are they? I've put hardly any effort into memorising them, but by just doing past papers you just get to know what they are.
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