[MrBlackwood]

I am stuck on the following question and how to work out the two unknowns. If anyone could point me in the right direction, i would be grateful!

'An experimenter wishes to calculate the mass of an object and sets up an experiment to do so. She makes measurements of the force F ( in Newtons) and acceleration a (in ms-2) and plots a graph, from which a straight line results. She measures the gradient of the line to be 4.51.

Assuming that the equation F = 3.79p.m.a is valid, where p = 2.90, calculate the value of m which she measures. [7 marks]'

[Pkysam]

This question seems poorly worded to me. Is this literally how it is written? No diagram? Are we to assume that force is plotted on the x axis, since it's presumably being applied and acceleration measured? The question states they are both "measured"... strikes me as a somewhat odd experiment!

Anyway, I'm guessing the two bits of information are the relationship between a and F in para 1 (a = 4.51F presumably) and the equation at the bottom F = 10.99ma.

[MrBlackwood]

(Original post by Pkysam)
This question seems poorly worded to me. Is this literally how it is written? No diagram? Are we to assume that force is plotted on the x axis, since it's presumably being applied and acceleration measured? The question states they are both "measured"... strikes me as a somewhat odd experiment!

Anyway, I'm guessing the two bits of information are the relationship between a and F in para 1 (a = 4.51F presumably) and the equation at the bottom F = 10.99ma.

Yes. The question is exactly copied, and is from the previous years exam, we have no diagrams, just the question. Hence you can probably see why I am a bit confused. But yes I guessed to have to assume that force is plotted on the X axis.

[Pkysam]

In that case, do you now have the answer? Can I ask what the paper was?

[MrBlackwood]

(Original post by Pkysam)
In that case, do you now have the answer? Can I ask what the paper was?

I'm struggling to find one if I am honest!

[The Polymath]

(Original post by MrBlackwood)
I am stuck on the following question and how to work out the two unknowns. If anyone could point me in the right direction, i would be grateful!

'An experimenter wishes to calculate the mass of an object and sets up an experiment to do so. She makes measurements of the force F ( in Newtons) and acceleration a (in ms-2) and plots a graph, from which a straight line results. She measures the gradient of the line to be 4.51.

Assuming that the equation F = 3.79p.m.a is valid, where p = 2.90, calculate the value of m which she measures. [7 marks]'

The gradient of the line is F/a = 4.51.
p = 2.90

F = 3.79 x p x m x a
F/a = 3.79 x 2.90 x m

4.51 = 3.79 x 2.90 x m

m = 0.410 kg to 3.s.f.

Edit: The Force *must* have been on the y-axis, as if it was on the x, this would mean the gradient was a/F = a/ma = 1/m, which is not a straight line, but rather a reciprocal function. So F/a is definitely 4.51

Lovely question actually

[MrBlackwood]

(Original post by Junaid96)
The gradient of the line is F/a = 4.51.
p = 2.90

F = 3.79 x p x m x a
F/a = 3.79 x 2.90 x m

4.51 = 3.79 x 2.90 x m

m = 0.410 kg to 3.s.f.

Edit: The Force *must* have been on the y-axis, as if it was on the x, this would mean the gradient was a/F = a/ma = 1/m, which is not a straight line, but rather a reciprocal function. So F/a is definitely 4.51

Lovely question actually

THANK YOU!

It was the f/a = M that I forgot! Minor brain freeze. I was like, how can you have two unknowns and be required to work out an exact answer!

[The Polymath]

(Original post by MrBlackwood)
THANK YOU!

It was the f/a = M that I forgot! Minor brain freeze. I was like, how can you have two unknowns and be required to work out an exact answer!

If it was a 7 mark question, do you reckon you would have had to have stated (lovely tense there, dunno what you'd call it) the thing about it being F/a and not a/F.

[Pkysam]

(Original post by Junaid96)
The gradient of the line is F/a = 4.51.
p = 2.90

F = 3.79 x p x m x a
F/a = 3.79 x 2.90 x m

4.51 = 3.79 x 2.90 x m

m = 0.410 kg to 3.s.f.

Edit: The Force *must* have been on the y-axis, as if it was on the x, this would mean the gradient was a/F = a/ma = 1/m, which is not a straight line, but rather a reciprocal function. So F/a is definitely 4.51

Lovely question actually

Hang on... if the gradient is 1/m, which is a constant (since m is a mass and not changing) then this is still a straight line and not reciprocal at all surely?

[The Polymath]

(Original post by Pkysam)
Hang on... if the gradient is 1/m, which is a constant (since m is a mass and not changing) then this is still a straight line and not reciprocal at all surely?

You may be right.. Might have jumped too quickly to the reciprocal argument upon seeing the 1/m.

[Pkysam]

Sorry to be the bearer of bad news! I stand by my assertion that it's a bad question!