## O-Level Physics

PSLE marks the graduation of Primary school students and their entry into Secondary schools as teenagers. Discuss all issues about Secondary schooling here.

### 2013 Physics O Level Paper 1

Hi there ,

To students taking 2013 Physics O Level Paper 1, do take note of the following. Given what has been tested in Paper 2 already, we can hypothesize the concepts that may be tested in Paper 1, as follows:

1) Reading of vernier caliper, micrometer, ticker tape, pendulum
2) Kinematics (graphs) and terminal velocity concepts
3) Forces calculation (Net F=ma)
4) Moments calculation & stability concepts
5) Mass, weight, density (and inertia)
6) Pressure: Barometer, manometer, hydraulic press (P=F/A, P=hpg)
7) Temperature (e.g. thermocouple), Brownian motion concepts
8) Heat capacity & latent heat (graphs, concepts, calculations)
9) Reflection, refraction & TIR, Lenses
10) Waves: v = fλ calculations, concepts, graphs
11) EM waves conceptual understanding
12) Sound: calculations. i.e. echo, graphs, pitch & loudness, ultrasound
13) Current electricity: formulae, series & parallel, brightness of bulbs
14) D.C circuits: potential divider, LDR, thermistor, potentiometer
15) Electromagnetism: Fleming’s LH rule, right hand grip rule, D.C motor
16) EMI: Lenz’s law, A.C generator, transformer, power transmission
17) CRO displays: Time-based on switched off or on (d.c input, a.c input)

All the best!

Warm regards,
http://www.tuitionphysics.com

TuitionPhysics.com
YellowBelt

Posts: 27
Joined: Sun Aug 07, 2011 5:14 pm
Total Likes: 0

### physics question on reflection

can someone help me with this physics question. What is the characteristic of the image formed by the periscope with convex mirror on top and plane mirror at the bottom?
Thanks

sunnymoon
OrangeBelt

Posts: 89
Joined: Sat Nov 05, 2011 8:06 am
Total Likes: 0

### Re: physics question on reflection

sunnymoon wrote:can someone help me with this physics question. What is the characteristic of the image formed by the periscope with convex mirror on top and plane mirror at the bottom? [img]
Thanks

I. An image in a mirror is vitual. A virtual image is one that cannot be focussed on a screen.
Suppose you just have a flat (plane) mirror on a wall. The image seems to be behind the wall. There is no light passing through that point. If you put a screen there, no image would focus on the screen. So it is a virtual image. Having an additional convex mirror does not change the nature of the image being virtual. A convex mirror also produces virtual images.

II. The image is upright. Convex mirrors always produce upright images. (By the way concave mirrors can either produce an upright or inverted image depending on where the object is with respect to the focal point, but convex mirrors always give an upright image)

III. The image is not larger than the object. The image is smaller than the object. The purpose of the convex mirror is so that the bus driver can see a big field of view. This is the same feature of side mirrors on cars. The curvature of the mirror makes large objects appear as smaller images.

I will include a file with some ray diagrams for convex mirrors. You can see the images as smaller, upright and virtual……

So choice A is the answer.

Dr.Daniel
GreenBelt

Posts: 147
Joined: Sun Dec 26, 2010 12:28 am
Total Likes: 2

### O-Level Physics

Thank you once again.

lunamoon
KiasuNewbie

Posts: 2
Joined: Thu Jun 05, 2014 12:28 pm
Total Likes: 0

Thank you once again.

Qns 16:
If the box is more dense than the liquid, it will sink.
If the box is less dense than the liquid, it will float.

In "R", since the box sink, it means it has a larger density than the liquid. So the liquid R has the smallest density.

Compare the remaining 3, the box in "Q" has the biggest surface floating above the liquid, hence the liquid "Q" has the biggest density.

Hope it is clear.

koguma
BlueBelt

Posts: 401
Joined: Fri Oct 29, 2010 3:20 pm
Total Likes: 1

Qns 17:

Clockwise moment : 0.8m*5N = 4 Nm
Anticlockwise moment : 1.5m * 4N = 6 Nm

Anticlockwise moment is bigger than Clockwise moment by 2 Nm,
so you need 2 Nm for the clockwise moment to balance the system,

koguma
BlueBelt

Posts: 401
Joined: Fri Oct 29, 2010 3:20 pm
Total Likes: 1

### Re: physics question on reflection

Thanks Dr Daniel for answering my question

sunnymoon
OrangeBelt

Posts: 89
Joined: Sat Nov 05, 2011 8:06 am
Total Likes: 0

### Re: physics question : work done

Can someone help me with the following questions? Thanks
A basket is being carried by a boy at a constant height above the ground. Is there work done?

sunnymoon
OrangeBelt

Posts: 89
Joined: Sat Nov 05, 2011 8:06 am
Total Likes: 0

Hi Luna

For Question 12, the reason you answered 0 is because you assumed all surfaces (including the surfaces of the boxes) are frictionless.
Hence, the box Q can be pulled from under without affecting P?

If the box Q can be pulled from under without affecting P, the answer wouldn't be 0 too. Weight of P acts on it causing it to free fall.

Thank you once again.

ilovegoodkopi
KiasuNewbie

Posts: 8
Joined: Tue Jun 17, 2014 4:09 pm
Total Likes: 1

### Re: physics question : work done

If the basket continues to be at constant height (from ground) --> no change in its GPE
If the basket continues to be at constant speed --> no change in its KE

So no work done on basket by the boy then.....

sunnymoon wrote:Can someone help me with the following questions? Thanks
A basket is being carried by a boy at a constant height above the ground. Is there work done?

ilovegoodkopi
KiasuNewbie

Posts: 8
Joined: Tue Jun 17, 2014 4:09 pm
Total Likes: 1

Next