Q&A - P3 Science

[Lynn2]

Earlier part of the day, I did try to read up on this topic, the book mention something like cross section of the object…which I cannot really digest.

[tianzhu]

Lynn2:

Earlier part of the day, I did try to read up on this topic, the book mention something like cross section of the object...which I cannot really digest.

Hi

The simplest way to see what is a cross section of an object. Take an apple and cut into two halves, look at the white portion, which is the cross section of an apple.

http://aggie-horticulture.tamu.edu/syllabi/201h/ediblebotany/applecut.html

[Lynn2]

Hi Tianzhu


Thanks for explaining cross section.May I know how to apply to the question as below.thanks

rgds

Lynn2:

Hello all

Could not sleep at this wee hour and is thinking how to go about doing this, can anyone help...

http://www.wendykoh.com/08/primary4-acssa2-science.pdf
Question 40

I dont understand how different angle affect the postion of the shadow.For this case, I totally cannot see it.

thanks

[tianzhu]

Hi


In answering this question, we need to understand the concept of shadow.
A shadow is made when an object blocks light. Opaque objects make dark shadows. Translucent objects make faint shadows. A transparent object will not make any shadow, as light will pass straight through it.

In this question, focus on the opaque conical shape. From angle 1, you’ll get a dark circle. As from angle 2, you’ll see a dark triangle.

Try to find some conical shapes in your house eg an ice cream cone, some toys which are conical in shapes. Play with them and try to see the elevations.

Have a nice day

[Lynn2]

Thanks Tianzhu



So, for angle 2, the answer will be just one traiangle instead of what the answer in the WS?That is together with object 1 being drawn in as answer?

thanks


rgds
Lynn2

[tianzhu]

Hi


Based on the concept that a transparent object will not make any shadow, as light will pass straight through it, only a triangle can be seen.

[Lynn2]

Thanks, Tianzhu.


Hey Folks

I have more questions to ask...help.

1Which of the following statement is /are false?
A The temperature of an object tells us how cold or hot an object is.
b The temperature of an object is a measure of the amount of heat of the object has.
c Glass is used to make a clinical thermometer because it is a good conductor of heat.

Answer is B and c only.But my girl think its A only as she thinks that glass is a bad conductor of heat.

May I know what is your answer?

2 Mrs Smith puts a kettle of water to boil.A steel sheet,clamped to a retort stand is placed directly above the opening of the mouth of the kettle.A heating element is used to maintain the temperature of the steel sheet at 100 deg celsius.

When the water started to boil, which of the following statements correctly describe what would happen?
1 The steel sheet expanded.
2Tiny water droplets could be seen on the underside of the steel sheet,

Answer is 1 Just wonder why is it not 2?

20 A few spoonfuls of salt were added into the beaker of crushed ice.Which one of the following graph correctly shows how the readings of thermometers p and W change when the salt was added?

Sorri, cant scan the graph cos no scanner.May i just write it down.

Answer : Temperature of p drop as mins go on,temperature of q, drop from zero to freezing point and go up but still below zeros degree.

Can someone explain how the salt affect the water level and temperature ?thanks everyone...

Cheers

tianzhu:

Hi

Based on the concept that a transparent object will not make any shadow, as light will pass straight through it, only a triangle can be seen.

[Lynn2]

Hello all, am trying to work out some MCQ with my gal, can cross check on …


1 We can clearly feel our heartbeat at our…

ans : wrists,temples and neck.

May I know why temples is one of the point?

2 What will happen if we have a weak heart?

thanks

[tianzhu]

[quote]1Which of the following statement is /are false?

A The temperature of an object tells us how cold or hot an object is.
b The temperature of an object is a measure of the amount of heat of the object has.
c Glass is used to make a clinical thermometer because it is a good conductor of heat.[/quote]
Hi
Heat is a form of energy that makes an object hot.It is a measure of the amount of heat of the object has.

Glass is used in clinical thermometers because it is transparent. Temperature readings can be taken off quickly and easily from the thermometer.

The question asked for statements which are false. Hence option (b) and (c) are logical.

[tianzhu]

[quote]2 Mrs Smith puts a kettle of water to boil.A steel sheet,clamped to a retort stand is placed directly above the opening of the mouth of the kettle.A heating element is used to maintain the temperature of the steel sheet at 100 deg celsius.


When the water started to boil, which of the following statements correctly describe what would happen?
1 The steel sheet expanded.
2Tiny water droplets could be seen on the underside of the steel sheet,[/quote]
Hi
The key point is A heating element is used to maintain the temperature of the steel sheet at 100 deg celsius.

Condensation takes place when steam touches a cooler surface. Therefore option (1) is correct.