PSLE SCIENCE - Bluetree€¦ · The diagram shows Object B balanced by magnets A and X. a) In the...
Transcript of PSLE SCIENCE - Bluetree€¦ · The diagram shows Object B balanced by magnets A and X. a) In the...
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PSLE SCIENCE
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A force is a push or a pull, when we push or pull an object,
we are applying a force on it.
Frictional Force, Magnetic Force,
Gravitational Force, Elastic Spring Force
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Frictional force between surface of
_____ and the surface of _____
-Slows down moving objects
-Stops moving objects
-Opposes movement
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The box TOOK A LONGER
TIME to fall after the
parachute is opened
The object DOES NOT move or
difficult to move
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Frictional force between the
surface of ______ and the surface
of______ is MORE/GREATER than
the ________force acting on the
object
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1. Applying lubricants such as oil and grease,
especially onto moving parts of machines to reduce
wear and tear, so that the machine lasts longer.
2. Rollers, ball bearings or wheels help to reduce
friction to move heavy objects.
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Bryan set up an experiment as shown below. He used a spring balance to pull two
identical wooden blocks across ramp A and ramp B. Both ramps are made of different
materials.
a) Bryan noticed that more force was required to move the wooden
block across ramp A than ramp B. Give a reason for his observation.
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Bryan set up an experiment as shown below. He used a spring balance to pull two
identical wooden blocks across ramp A and ramp B. Both ramps are made of different
materials.
Ans) The surface of A is rougher than B, hence there is more
frictional force between the surface and the box opposing the
pull force exerted on the box.
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Bryan repeated his experiment using ramp A as shown below. He measured the force
needed to pull the wooden block using a different angle x. The graph shows his results.
b) State how the pulling force changes with angle X.
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Bryan repeated his experiment using ramp A as shown below. He measured the force
needed to pull the wooden block using a different angle x. The graph shows his results.
Ans) As angle X of the ramp increase, the pulling force
exerted on the box also increases.
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A magnet is an object made of iron or steel. It can
attract (pull) or repel (push) magnetic objects.
• Attract magnetic objects
• Has 2 poles where attraction is the strongest (North and South Poles)
• Unlike poles attracts each other and like poles repel each other
• Comes to rest in the North-South Direction when freely suspended
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1. Stroking a magnetic object with
a magnet permanent magnet
2. Use electricity to magnetize a
magnetic object through electro
magnetization.
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The diagram shows Object B balanced
by magnets A and X.
a) In the diagram, fill in N and S to show
the poles of magnet X.
b) Explain how Object B is balanced by
magnet A
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The diagram shows Object B balanced by
magnets A and X.
a) In the diagram, fill in N and S to show
the poles of magnet X.
b) Explain how Object B is balanced by
magnet A
Ans: The magnetic attraction force
between magnets A and X is the same as
the gravitational force acting on object B.
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C) Object B is replaced by Object C with a
mass of 60g. Magnet X is also replaced by
magnet Y.
To balance Object C, fill in 'N' and 'S' to
show the poles of magnet Y.
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C) Object B is replaced by Object C with
a mass of 60g. Magnet X is also
replaced by magnet Y.
To balance Object C, fill in 'N' and 'S' to
show the poles of magnet Y.
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Depends on : Height and Mass
Depends on : Weight and Mass
(Not to be confused with Gravitational Potential Energy)
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a) Mr Aziz found that it requires
more effort to climb up the stairs
compared to going down.
Give a reason for your answer.
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Ans: More effort is required when
going up because he is going against
the direction of gravity.
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b) The diagram below shows a flight of wooden stairs in an elderly nursing home
i) What is the function of the rough strips of material which are mounted on the
stairs? Explain your answer clearly.
ii) After several years of use, it was observed that some patients would slip
occasionally as they went up or down the stairs. What could be a possible
reason for this?
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b) The diagram below shows a flight of wooden stairs in an elderly nursing home
i) What is the function of the rough strips of material which are mounted on the
stairs? Explain your answer clearly.
Ans: The function of the rough strips is to increase the frictional force between the
surface of the stairs and surface of the feet on the elderly. This will prevent the
elderly from slipping and falling.
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b) The diagram below shows a flight of wooden stairs in an elderly nursing home
ii) After several years of use, it was observed that some patients would slip occasionally
as they went up or down the stairs. What could be a possible reason for this?
Ans: After several years, due to wear and tear, the strips could become smoother. This reduces the frictional force between the strip and the feet, hence increasing the chances of slipping.
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A Force exerted by a spring when it
is stretched or compressed.
What can an elastic object do?
1. Change shape when force is applied
2. Return to its original shape when applied force is removed.
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The diagram below shows a bow and arrow and when the string of the bow was pulled back.
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The diagram below shows a bow and arrow and when the string of the bow was pulled back.
Ans: Gravitational Force
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When the string was released, the arrow travelled in the path as shown below
before hitting the ground at point K.
b) In terms of forces, explain the movement of the arrow from the point it was
released at A till it hit the ground at B.
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When the string was released, the arrow travelled in the path as shown below
before hitting the ground at point K.
Ans: The push force exerted on the arrow pushes it forward but it is
weaker than the gravitational force exerted on the arrow hence the arrow was pulled down to the ground eventually.
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When the string was released, the arrow travelled in the path as shown below
before hitting the ground at point K.
c) The activity was repeated with an arrow of a greater mass. Explain how this will affect the movement of the arrow.
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When the string was released, the arrow travelled in the path as shown below
before hitting the ground at point K.
Ans: The arrow will hit the ground faster. The increased mass of the
arrow will result in more gravitational force acting on the arrow and pulled it down to the ground more.