Q&A - PSLE Science

[enreachlearningcentre]

[quote]Chan09 wrote:

Need some help as don't understand why this is false?

When a ball reaches its max height, the force of gravity acting on the ball is the greatest.

Tks[/quote]Hi, this qn relates to the principle of conservation of energy.
Consider a ball being thrown upwards, the total energy is simply the sum of Grav. Potential Energy(GPE) + Kinetic Energy(KE)= constant
GPE depends on mass & height. KE depends on mass & velocity.
As ball goes up higher, KE is being converted to GPE in order that total energy is a constant.
So at max height, KE is zero(as ball's velocity is zero at that instant) giving GPE to be greatest.
This max GPE is the result of max grav. force acting on the force.

Hope it helps

[kitty2]

Please help with these questions :?: :thankyou:


1)There's a herd of elephants.How do they adapt to escape from their predators?Explain why this method of adaptation is effective?

2)Describe the typical habitat of a polar bear.How is the polar bear adapted for surviving in its habitat?List 3 ways.

3) Describe the typical habitat of a grizzly bear.The grizzly bear and the polar bear are both adapted to survive in a cold enviroment.What is the difference between the climate conditions of the grizzly bears' habitat and the polar bear's habitat?

4) How is grizzly bear adapted to survive in its habitat.List 2 ways.

5) Apart from the grizzly bear,name another animal that has a similar behavioural adaptation.

[elkniwt]

Hi charsen,


Thank you very much!!! I like your explanation. Very clear.
:thankyou:

My dd is asking if the question is referring the energy conversion for the action of turning on the fan ???

Chemical Potential Energy (your body) -> Kinetic energy (the action turning on switch) -> then we don't know already ??

charsen:

elkniwt:

Hello,

Pls help.

What is the energy conversion for \"switching on the ceiling fan? :?:

Thanks in advance.

Hi
(ANS)Electrical energy---->Kinetic Energy+heat energy+sound energy

The electrical energy in the main sockets converts into kinetic energy when you turn on the ceiling fan as the motor in the ceiling fan is moving.Heat energy is produced between the motor and the blades of the fan.You would hear sounds from the fan won't you?Hence,this shows that sound energy is produced.
Hope this explanation works.
Cheers

[Robertpattinsonidle]

elkniwt:

Hi charsen,


Thank you very much!!! I like your explanation. Very clear.
:thankyou:

My dd is asking if the question is referring the energy conversion for the action of turning on the fan ???

Chemical Potential Energy (your body) -> Kinetic energy (the action turning on switch) -> then we don't know already ??

charsen:

[quote=\"elkniwt\"]Hello,

Pls help.

What is the energy conversion for \"switching on the ceiling fan? :?:

Thanks in advance.

Hi
(ANS)Electrical energy---->Kinetic Energy+heat energy+sound energy

The electrical energy in the main sockets converts into kinetic energy when you turn on the ceiling fan as the motor in the ceiling fan is moving.Heat energy is produced between the motor and the blades of the fan.You would hear sounds from the fan won't you?Hence,this shows that sound energy is produced.
Hope this explanation works.
Cheers

[/quote]if the fan is the battery operated one, then it is:
chemical potential energy to electrical energy to kinetic energy+ sound energy+ heat energy
chemical potential in our body does not count if they are talking about energy conversion in fan and not from when we switch the fan on. anyways, the chemical potential energy does not transfer to the kinetic energy in the switch's movement. it starts only from electricity in the close circuit

[Alarmchain]

Hi elkniwt,


This is yet another excellent example of an ambiquous question.

Especially for this topic of energy conversion, my DD often gets confused as to what degree of details is expected? In this instance, is it Chemical Potential Energy of Body = KE of finger + KE of switch + Sound Energy? Or is it as pointed out by Charsen?

I would think it is the latter, but in expecting the children to be detailed and specific with their answers, I have often seen questions which are NOT specific and detailed to begin with … sigh …

In my effort to help my DD maintain her interest and, more importantly, her confidence in her reasoning skills, I will listen to her logic behind her explanation and if it makes sense, I will reassure her to ignore the marks and explain why I think her answer is right or wrong.

No choice, would rather lose this battle than the war for knowledge.

Cheers!

[Robertpattinsonidle]

Alarmchain:

Hi elkniwt,


This is yet another excellent example of an ambiquous question.

Especially for this topic of energy conversion, my DD often gets confused as to what degree of details is expected? In this instance, is it Chemical Potential Energy of Body = KE of finger + KE of switch + Sound Energy? Or is it as pointed out by Charsen?

I would think it is the latter, but in expecting the children to be detailed and specific with their answers, I have often seen questions which are NOT specific and detailed to begin with .... sigh .....

In my effort to help my DD maintain her interest and, more importantly, her confidence in her reasoning skills, I will listen to her logic behind her explanation and if it makes sense, I will reassure her to ignore the marks and explain why I think her answer is right or wrong.

No choice, would rather lose this battle than the war for knowledge.

Cheers!

for what my teacher told me[i am currently a psle student], my teacher said to answer the question directly; in a way that we are actually in a straight forward manner and what is accepted
in this cas, what we need to say is this:
electric energy in the complete circuit when switched on converts to kinetic energy when the fan spins + unwanted energy when the fan spins, such as heat+sound energy.
this is it, according to my teacher.
in specific qsns it will be stated :'explain what will happen in energy conversion from the moment that the john's hand touches the switch.as
i said before, chemical potential energy in john's hand does not change to electric energy in circuit because john's hand is giving a force and not an energy.

cheers! :imcool:

[Alarmchain]

Thank you.


I think it is great that you kids are helping one another prepare for your exams. Very unselfish and magnanimous behaviour. You all should nominate each other for the EAGLES Award!

Cheers!

[Robertpattinsonidle]

Alarmchain:

Thank you.


I think it is great that you kids are helping one another prepare for your exams. Very unselfish and magnanimous behaviour. You all should nominate each other for the EAGLES Award!

Cheers!

thanks. two brains is always better than one. here, everyone learns, so it is good to share your knowledge. by the way, any psle students or their parents here? i am a psle student too so please give me some advice!! :thankyou:

[charsen]

kitty2:

Please help with these questions :?: :thankyou:


1)There's a herd of elephants.How do they adapt to escape from their predators?Explain why this method of adaptation is effective?
>>> When the elephants in the herd is disturbed by predators,they would attacks a group to protect the herd.Thus,this method is an effective method of adaptation for protection.

2)Describe the typical habitat of a polar bear.How is the polar bear adapted for surviving in its habitat?List 3 ways.
>>> Polar bears live in the arctic region where it is cold all the time.The polar bears have thick fur and a layer of fat,which are heat insulators that helps to keep the body warm.Polar bears hibernate and conserve energy to survive through the cold winter.It has black skin beneath its white fur that allows it to absorb heat from sunlight and keep the body warm.

3) Describe the typical habitat of a grizzly bear.The grizzly bear and the polar bear are both adapted to survive in a cold enviroment.What is the difference between the climate conditions of the grizzly bears' habitat and the polar bear's habitat?
>>>> The typical habitat of a grizzly bear are cold at certain times of the year while that of a polar bear's habitat which is cold all the time.

4) How is grizzly bear adapted to survive in its habitat.List 2 ways.
>>> It grows thick winter fur coat to keep the body warm.It hibernates and conserve energy to survive during cold climate.

5) Apart from the grizzly bear,name another animal that has a similar behavioural adaptation.

>>> Chipmunk/bat/skunk in the way they hibernate .

[kitty2]

charsen:

kitty2:

Please help with these questions :?: :thankyou:


1)There's a herd of elephants.How do they adapt to escape from their predators?Explain why this method of adaptation is effective?
>>> When the elephants in the herd is disturbed by predators,they would attacks a group to protect the herd.Thus,this method is an effective method of adaptation for protection.

2)Describe the typical habitat of a polar bear.How is the polar bear adapted for surviving in its habitat?List 3 ways.
>>> Polar bears live in the arctic region where it is cold all the time.The polar bears have thick fur and a layer of fat,which are heat insulators that helps to keep the body warm.Polar bears hibernate and conserve energy to survive through the cold winter.It has black skin beneath its white fur that allows it to absorb heat from sunlight and keep the body warm.

3) Describe the typical habitat of a grizzly bear.The grizzly bear and the polar bear are both adapted to survive in a cold enviroment.What is the difference between the climate conditions of the grizzly bears' habitat and the polar bear's habitat?
>>>> The typical habitat of a grizzly bear are cold at certain times of the year while that of a polar bear's habitat which is cold all the time.

4) How is grizzly bear adapted to survive in its habitat.List 2 ways.
>>> It grows thick winter fur coat to keep the body warm.It hibernates and conserve energy to survive during cold climate.

5) Apart from the grizzly bear,name another animal that has a similar behavioural adaptation.

>>> Chipmunk/bat/skunk in the way they hibernate .

:thankyou: