Lower Secondary Science
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Gems:
A is the best choice, although there are issues with the question.Anyone can help?
2.A car moves along a smooth road with its engine exerting a constant force. What change will occur to the car?
a. Its speed will increase.
b. Its acceleration will increase.
c. Its mass will increase.
d. Its direction of movement will change.
\"smooth road\" I interpret as meaning no friction . Usually \"smooth\" means no friction, while \"rough\" indicates friction.
The only possible interpretation of the question given the MCQ choices is that there is a constant driving force and no friction. So that being the case there will be constant acceleration and an increase in speed.
But there is a problem with the question. It is friction between the wheels and the road that allows the driving force to move the car forward. (standard O-Level question by the way). If a car has its wheels on an oil slick and there is no friction, the wheels cannot grab onto the road. The wheels will just turn and there will be no driving force behind the car.
Also, the main contribution to friction opposing the motion in the case of a car is friction with the air.
So a clearer question would be \"a block is pushed on a smooth surface by a constant force.......\"
no issue with wheels, and air friction is minimal just pushing a block along a surface (low speed implied compared to a car) -
Sorry, we still don’t understand the 1st question. How to derive at 1.39? Multiply out could not get the area too. Thanks.
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Hope to get an answer by today…
Viruses can be classified on the basis of _______
I. Nucleic acid type
II. Nature of host
III. Capsid symmetry
IV. Presence or absence of an envelope
(a) I and II only
(b) III and IV only
I, II and III only
(d) All of the above
Answer is (d). Why? I, II and II ds can understand. But (IV) - he wants to know what the envelope is referring to. If it’s referring to nuclei, then it’s wrong because all viruses have no nucleus. -
An envelope on a virus is on the exterior. The outermost layer on some viruses. It is made up of material from the host cell membrane. Some viruses like influenza use this strategy, but other viruses do not have an envelope. So it can be used as a way of classifying a virus.
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Gems:
Sorry, we still don't understand the 1st question. How to derive at 1.39? Multiply out could not get the area too. Thanks.
360,000 Pa = 5N/Area
Area = 5N/360,000Pa = 1.39 X 10-5 square meters
Pa is N/m2
there are 100 cm in 1 meter, but 10000 cm2 in a m2. So to convert to cm2 multiply by 10,000 to get 0.139 cm2. -
Dr.Daniel:
An envelope on a virus is on the exterior. The outermost layer on some viruses. It is made up of material from the host cell membrane. Some viruses like influenza use this strategy, but other viruses do not have an envelope. So it can be used as a way of classifying a virus.
Thank you., Dr Daniels....
Would appreciate it as I need help for the following questions:
1,The enzyme in pineapple soften meat before cooking. What enzyme function in a similar way in human body? Just to confirm if the answer is 'protease' since meat is protein? or should it by amalyse?
2.Which of the following is true?
a) Bacteria can produce spores.
b) fungi can reproduce by sexual reproduction
c) All viruses have the same capsid symmetry.
Is the answer c)? -
Verysuperkiasu:
Right, protease. Protease in the human body works on proteins (found in meat), amalyse breaks down starch into sugars.
1,The enzyme in pineapple softens meat before cooking. What enzyme functions in a similar way in the human body? Just to confirm if the answer is 'protease' since meat is protein? or should it by amalyse? -
Verysuperkiasu:
Were they asking which is not true?
2.Which of the following is true?
a) Bacteria can produce spores.
b) fungi can reproduce by sexual reproduction
c) All viruses have the same capsid symmetry.
Is the answer c)?
a) true
b) true
c) not true -
Dr.Daniel:
ds can't recall - it was one of his exam questions. BTW, I thought only fungi reproduce by spores.
Were they asking which is not true?Verysuperkiasu:
2.Which of the following is true?
a) Bacteria can produce spores.
b) fungi can reproduce by sexual reproduction
c) All viruses have the same capsid symmetry.
Is the answer c)?
a) true
b) true
c) not true
Thanks anyway! -
Fungi use spores, but some bacteria do also - they are called endospores. Some were found in the tombs of the Eqyptian Pharoahs and when placed in the right environment, they produced the bacteria again. So they are amazingly resilient and can survive for even thousands of years.
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