***JC 2014 Technology Papers - Wed. June 18th 2014 - all levels***

coolerboy

Technology (OL and HL)
Wednesday June 18th 2014




All discussion and questions about Technology papers goes here, following the exam. Please do not post predictions or discussion here before the exam.

Usual rules apply. Anyone slagging off another poster about the level they did, or a mistake they made, will be banned for the duration of the exams.

Please keep off-topic chat elsewhere.

Good luck all.

spurious

Bumping to bring it up to the top of the page

coolerboy

Does anyone here do technology. If u do what u get for the mechanisms question caluation I got 1 minute but I think it was 45 seconds

nanook5

coolerboy wrote: »

Does anyone here do technology. If u do what u get for the mechanisms question caluation I got 1 minute but I think it was 45 seconds

I do it but I did electronics :P

danm14

The one with the how long the motor takes to move 30mm? 6 seconds I got. I'd be fairly sure you're wrong I'm afraid because it wouldn't be that likely itd take a minute to move something just over an inch :P Still of course it's an exam, not real life so it's possible I'm wrong and you're right!

Did you do Q6 (Control Systems)? If so what was the logic gate A? I said a NOT gate, because it was the only one with one input, but it didn't seem like it would work.
Our teacher told us not to do that question but I did every past control systems question back till 2001 and corrected with the mark scheme and got full marks, so I'm not sure of the answers - we were never taught it, it just made sense to me immediately.

Did everyone in your exam leave early today? By the time the exam was over in my centre, everyone bar myself and one other lad had left about fifteen minutes early, even a person who gets extra time to finish as a reasonable accomodation. Whether that was because it was their last exam or because they were genuinely finished early I don't know, but I'd be assuming the former :P

danm14

Motor spins at 150RPM (rotations per minute)
Attached to worm (1 tooth per rotation)
Worm spins at 150RPM
Attached to worm wheel (20 teeth)
Wheel spins at 7.5RPM (150/20=7.5)
15 teeth = 30mm
15 teeth / 7.5 RPM = 2

I get 2 minutes now.... Where I got 6 seconds from I don't know!
If someone who understands gear calculations could do this out:

Motor @ 150RPM with worm.
Worm attached to Worm wheel 20 teeth
Worm wheel acts as Pinion attached to Rack - 5 teeth = 10mm
How long for the rack to move 30mm?

2014 Technology Section B Question 2(b), specifically part (iii)

coolerboy

150÷10=15
Moves 1teeth every rotation
10mm=5 teeth
30mm=15 teeth
1 minute

danm14

coolerboy wrote: »

150÷10=15
Moves 1teeth every rotation
10mm=5 teeth
30mm=15 teeth
1 minute

Why are you dividing by 10?
I see it now as: 150 teeth per minute on the worm wheel = 150 teeth per minute on the rack
150teeth/15teeth = 10 teeth
60sec/10sec = 6sec

coolerboy

danm14 wrote: »

Why are you dividing by 10?
I see it now as: 150 teeth per minute on the worm wheel = 150 teeth per minute on the rack
150teeth/15teeth = 10 teeth
60sec/10sec = 6sec

Worm wheel reduces speed by 10

danm14

coolerboy wrote: »

Worm wheel reduces speed by 10

That is wrong, it would depend on the number of teeth on the worm wheel how much the speed would be reduced. (In this case it's reduced by 7.5 however that is irrelevant here)

For every one rotation of the motor, one tooth on the worm wheel moves.

In sixty seconds, 150 teeth on the worm wheel move. This means that in 6 seconds, 15 teeth move. This moves the rack by 15 teeth (30mm)

coolerboy

danm14 wrote: »

That is wrong, it would depend on the number of teeth on the worm wheel how much the speed would be reduced. (In this case it's reduced by 7.5 however that is irrelevant here)

For every one rotation of the motor, one tooth on the worm wheel moves.

In sixty seconds, 150 teeth on the worm wheel move. This means that in 6 seconds, 15 teeth move. This moves the rack by 15 teeth (30mm)

Ok ok ok i get it know.........




(Sarcastically)