OCR Advancing Physics G492 ~5 June 2013~

liomeeringca,

Read the MS again, it says 169m^2s^-2 and the same for 900.

I just used v^2 = u^2 +2as, then rearrange for s.

I apologise, the reason they have those units is because they've been squared:
(m/s)^2 = (m^2/s^2)

(edited 10 years ago)

Reply 123

Original post by AndItsOllie

I know, it sucks!
Ok awesome! Are there any answers for the section C notes around?

I'm afraid not mate, I've got a few if you need them! Just ask :smile:

Reply 124

Original post by ArchieL

I apologise, the reason they have those units is because they've been squared:
(m/s)^2 = (m^2/s^2)

I understand now, thank you for your help :smile:

Reply 125

jacobfun

Original post by marseille_h

This might seem straightforward but I'm a bit confused:

A car has an acceleration of 0.86g. Calculate the time it takes to reach a velocity of 27m.s-1.
g=9.81

v=u+at
so t= (v-u)/a

is g=acceleration in this case and the acceleration of the car they give we take it as u and v=27 ?

Acceleration would be 0.86 x g, so 0.86 x 9.81. I assume you would take u as 0 and v as 27 and then use v=u+at to find t.

Reply 126

Original post by jacobfun

Acceleration would be 0.86 x g, so 0.86 x 9.81. I assume you would take u as 0 and v as 27 and then use v=u+at to find t.

which formula do we use to get acceleration and do 0.86 x g ?

Reply 127

Original post by marseille_h

which formula do we use to get acceleration and do 0.86 x g ?

No formula. 'g' is shorthand for the acceleration due to gravity (on earth) ~ 9.81ms^-2
=> an acceleration of 0.86g = (0.86)(9.81) = 8.4366 ~ 8.44

(edited 10 years ago)

Reply 128

Original post by ArchieL

No formula. 'g' is shorthand for the acceleration due to gravity (on earth) ~ 9.81ms^-2
=> an acceleration of 0.86g = (0.86)(9.81) = 8.4366 ~ 8.44

Oh i understand i thought it was a wierd unit. THANKS :smile:

Reply 129

How does everyone feel about potential dividers, thermisters and general electricity questions then? I'm bricking myself :frown:

Reply 130

Original post by ArchieL

How does everyone feel about potential dividers, thermisters and general electricity questions then? I'm bricking myself :frown:

None of this in unit 2 i think..

Reply 131

King Hotpie

Original post by liomeeringca

How would one calculate gravity from a set of results like that?

V^2=U^2+2as. F=ma, and the component for force in the direction of the ramp is gsin(theta). Therefore you can rearrange that to a=gsin(theta)
V^2=U^2 + 2gsin(theta)s. U=0, so you can rearrange it to g=V^2 divided by 2sin(theta)s

Reply 132

seharnaznaz

I saw someone had already answered this but I'm still unsure how to determine the value for g from v2= u2+2as

Can someone explain step by step please?

I hate all these maths based questions :frown:

Reply 133

Original post by ArchieL

How does everyone feel about potential dividers, thermisters and general electricity questions then? I'm bricking myself :frown:

Wasn't this G491?

Reply 134

Original post by marseille_h

None of this in unit 2 i think..

As far as I was aware, section C is a synopsis unit (of sorts?) :s-smilie:

Also I've got a question on it on some prelrelease questions set by the department at college, so I'd guess there might be a little on it? Don't get me wrong, I'd be over the moon if there wasn't! Haha

Reply 135

Original post by King Hotpie

Thank you so so much, :smile:

Reply 136

Original post by ArchieL

As far as I was aware, section C is a synopsis unit (of sorts?) :s-smilie:

I haven't looked a potential dividers in aaaaaaages! I really hope there's nothing on it, like you say D:

Reply 137

seharnaznaz

For the pre-release material on measuring the speed of light... why can it be assumed that the 'hotspot' where the chocolate melted is an antinode? :confused:

Reply 138

Original post by seharnaznaz

I saw someone had already answered this but I'm still unsure how to determine the value for g from v2= u2+2as

Can someone explain step by step please?

I hate all these maths based questions :frown:

With the trolley on the ramp, it has an acceleration, g, acting directly downwards. Construct a triangle with this force, another force c acting ϴ degrees to it originating from the floor (so they meet). Then add another from the top of grunning parallel to the slope. This cuts the line with c and forms a triangle. From the cosine rule, cosϴ=opp/hyp, so =a/g. Rearrange to get a=gsinϴ. (It's best to draw a diagram of all component forces, stripped down).

If we then substitute this into the equation v²=u²+2as with u=0, we get that result (v² =2.g.l.sinϴ). Also it's probably worth noting that plotting a graph with v^2 against sinϴ gets us with a gradient of 2.g.l

(edited 10 years ago)

Reply 139