July 22, 2019, 03:18:57 am

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#### JeKnYan

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##### Re: VCE Physics Question Thread!
« Reply #2265 on: June 10, 2019, 08:18:43 pm »
0
What's the recommendation on decimal places/sig figs in the exam? I've always been taught it's two, just asking for your two cents

#### Jackson.Sprigg

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##### Re: VCE Physics Question Thread!
« Reply #2266 on: June 11, 2019, 06:21:24 pm »
+2
I believe you should base your significant figures on the most inaccurate measurement in the question.

i.e. If the question gives you 3 values with 2, 3 and 4 sig figs respectively and you use all these values in your working. Then you can only say for certain that your answer is as accurate as the least accurate value you used. In this case it would be the 2 sig figs and so that is how many you would use in your final answer.
« Last Edit: June 11, 2019, 06:34:45 pm by Jackson.Sprigg »

#### Zealous

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##### Re: VCE Physics Question Thread!
« Reply #2267 on: June 14, 2019, 10:08:40 pm »
+1
I believe you should base your significant figures on the most inaccurate measurement in the question.

i.e. If the question gives you 3 values with 2, 3 and 4 sig figs respectively and you use all these values in your working. Then you can only say for certain that your answer is as accurate as the least accurate value you used. In this case it would be the 2 sig figs and so that is how many you would use in your final answer.

Yep, this approach works fine. If you are unsure, usually 3-4 sig figs is more than enough - I'm quite sure the exam markers accept answers within a certain tolerance.
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#### Terrapin

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##### Re: VCE Physics Question Thread!
« Reply #2268 on: June 18, 2019, 10:45:24 am »
0
A dodgem car of mass 200 kg is driven due south
into a rigid barrier at an initial speed of 5.0 m s−1.
The dodgem rebounds at a speed of 2.0 m s−1. It is
in contact with the barrier for 0.20 s. Calculate:
(a) the average acceleration of the car during its
interaction with the barrier
(b) the average net force applied to the car during
its interaction with the barrier.

#### Erutepa

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##### Re: VCE Physics Question Thread!
« Reply #2269 on: June 18, 2019, 08:15:52 pm »
+2
A dodgem car of mass 200 kg is driven due south
into a rigid barrier at an initial speed of 5.0 m s−1.
The dodgem rebounds at a speed of 2.0 m s−1. It is
in contact with the barrier for 0.20 s. Calculate:
(a) the average acceleration of the car during its
interaction with the barrier
(b) the average net force applied to the car during
its interaction with the barrier.
Before others weigh in on these questions, it is important that you give them a try first and write down what your current thought processes you have in regards to them. It is important to identify specifically what things you do know and what things you don't know so that you can better learn and people can better explain the questions to fit your own confusions.
And don't worry about getting things wrong - you won't be judged harshly at all.
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#### julia_atarnotes

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##### Re: VCE Physics Question Thread!
« Reply #2270 on: June 29, 2019, 11:56:28 am »
+2
What's the recommendation on decimal places/sig figs in the exam? I've always been taught it's two, just asking for your two cents

Hey! My past physics teacher was an examiner and he said that 2 decimal places is sufficient. Marks will only be taken off if the question asks you specifically to answer to the correct number of significant figures OR if you use too few significant figures eg. rounding 543.67 to 540. Using the "correct" number of significant figures can be tricky because a lot of physics constants that we are given only use 2-3 significant figures (eg. gravity, speed of light) which may not be enough to satisfy your examiner.

#### S200

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##### Re: VCE Physics Question Thread!
« Reply #2271 on: July 03, 2019, 11:27:54 pm »
+3
A dodgem car of mass 200 kg is driven due south
into a rigid barrier at an initial speed of 5.0 m s−1.
The dodgem rebounds at a speed of 2.0 m s−1. It is
in contact with the barrier for 0.20 s. Calculate:
(a) the average acceleration of the car during its
interaction with the barrier
(b) the average net force applied to the car during
its interaction with the barrier.
A.)
Acceleration is defined as the rate of change of velocity, or $\frac {V_I - V_F}{Time}$.
We're given the initial and the final velocities, and also the full time of the collision.
Hence, substitute the values and calculate...
$\frac{5-(-2)}{0.20} = 35ms^{-1}$ in a negative direction, or away from the barrier
Force is merely $Mass \times Acceleration$. The word 'average' is used to indicate that this is not an 'instantaneous' or precisely measured velocity. Thus, average Force is equal to the mass of the body multiplied by the average velocity over the defined time. $F = m \frac{(v_f - v_i)}{t}.$
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