PSLE SCIENCE

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

Frictional force between surface of

_____ and the surface of _____

-Slows down moving objects

-Stops moving objects

-Opposes movement

The box TOOK A LONGER

TIME to fall after the

parachute is opened

The object DOES NOT move or

difficult to move

Frictional force between the

surface of ______ and the surface

of______ is MORE/GREATER than

the ________force acting on the

object

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.

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.

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.

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.

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.

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

1. Stroking a magnetic object with

a magnet permanent magnet

2. Use electricity to magnetize a

magnetic object through electro

magnetization.

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

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.

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.

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.

Depends on : Height and Mass

Depends on : Weight and Mass

(Not to be confused with Gravitational Potential Energy)

–

a) Mr Aziz found that it requires

more effort to climb up the stairs

compared to going down.

Give a reason for your answer.

–

Ans: More effort is required when

going up because he is going against

the direction of gravity.

–

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?

–

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.

–

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.

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.

–

The diagram below shows a bow and arrow and when the string of the bow was pulled back.

–

The diagram below shows a bow and arrow and when the string of the bow was pulled back.

Ans: Gravitational Force

–

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.

–

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.

–

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.

–

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.