G6 Science Forces

FORCES

Forces

• Interactions can be caused by forces.

• A force is a push or a pull. 

Forces

• We can interact with the handle of a stroller to move the stroller forward.

• We exert a force on the handle to move the stroller away from us.

• This force is a push.

Forces

• We can interact with the handle of a car door to open the door.

• We exert a force on the handle to move the door towards us.

• This force is a pull.

Forces

• We exert forces on a wet piece of clothing when we twist it.

 

• This involves both a push and a pull.

Multiple Choice

Look at this activity.

Does this involve a push or a pull? Or both?

• PUSH

• PULL

Multiple Choice

What type of force is this man using to move his grocery cart forward?

• pull

• push

Multiple Choice

If these teams are pulling with the same amount of force, what will happen?

• The boy in blue will win.
• They will not move at all.
• The boy in red will win.
• Both will fall down.

Multiple Select

Look at this activity.

Does this involve a push or a pull? Or both?

• PUSH

• PULL

Open Ended

These are strong forces of nature at work.

What type of destruction can be caused by such forces?

Effects of a force

•We cannot see a force, but we can observe the effects of a force.

•A force can cause:

• a moving object to stop, change its direction, move faster or slower;

• a stationary object to start moving;

• an object to change its shape.

What are the effects of the forces involved in a game of tennis?

Types of force

•Some forces act on two objects that are in contact with each other.
Examples are frictional force and elastic spring force.

Some forces act on objects from a distance.
Examples are magnetic force and gravitational force

Frictional force

• Frictional force is a contact force.

• It is present when two surfaces are in contact.

• It can slow down or stop a moving object as it acts in the opposite direction of motion.

Frictional force

• The texture of a surface affects frictional force.

• There is greater frictional force between a moving object and a rough surface than between the object and a smooth surface.

• Thus, the moving object moves a shorter distance and more slowly on the rough surface.

Frictional force

• Frictional force helps to slow down or stop a moving object.

• It helps us to grip objects without dropping them.

• It prevents us from slipping and falling when we are walking.

Frictional force

•When we rub our hands together, there is friction between our palms.

•When we strike a matchstick against a matchbox, the frictional force between the matchstick and matchbox causes the matchstick to light up.

•Frictional force from the rubbing of sticks together can start a fire.

Frictional force

•Since frictional force opposes motion, it can cause moving objects to slow down.

•It also causes objects to overheat or wear out more easily.

Frictional force

•We can use lubricants such as oil, grease or water to reduce the frictional force between two surfaces.

•Wheels and ball bearings can also be used to reduce the frictional force between moving parts. f sticks together can start a fire.

Frictional force

Discussion: Frictional force

Drivers are encouraged to keep a safe distance from the vehicle ahead of theirs while driving. Why should they increase this distance on a rainy day or when the road is wet?

Discussion: Frictional force

Drivers are encouraged to keep a safe distance from the vehicle ahead of theirs while driving. Why should they increase this distance on a rainy day or when the road is wet?

Open Ended

Drivers are encouraged to keep a safe distance from the vehicle ahead of theirs while driving. Why should they increase this distance on a rainy day or when the road is wet?

Discussion: Frictional force

Frictional force also acts on objects in the air. How does the shape of the fighter jet plane enable it to fly faster than a helicopter?

Open Ended

Frictional force also acts on objects in the air. How does the shape of the fighter jet plane enable it to fly faster than a helicopter?

Multiple Choice

Which of the following is an example of friction that is helpful?

• Brakes used on a bike
• Tires from a car on the road
• Tread (uneven markings) on the bottom of your shoes

• All are examples that are helpful

Multiple Choice

The amount of friction depends on the weight of the objects acting on each other.

• True
• False

Multiple Choice

Rougher surfaces have ...

• greater friction
• less friction
• the same level of friction

Multiple Choice

If there is no friction, how would a marble traveling on a long, straight path be affected?

• The marble’s speed would decrease.
• The marble’s speed would increase.
• The marble would stop immediately. 
• The marble would remain at constant speed.

Multiple Choice

How does friction affect speed?

• more friction decreases speed
• more friction increases speed
• less friction decreases speed
• less friction doesn't affect speed

Multiple Choice

How do you lower the friction force?

• By a smooth surface
• By a rough surface
• By not pushing hard
• By pushing down

Multiple Choice

On which surface will a toy car travel the furthest?

• Carpet
• Polished Wood
• Ice

Multiple Choice

Engineers design airplanes so that friction is reduced.

What is one of the benefits from reducing friction?

• Less friction will allow the plane to fly more easily through the air and allows the plane to use less fuel.

• More friction will allow the plane to fly more easily through the air and allows the plane to use less fuel.

• Less friction will allow the plane to fly more easily through the air and allows the plane to use more fuel.

• Less friction will allow the plane to go up and down more easily.

Multiple Choice

Apollo 17 space ship was burned coming back into Earth's atmosphere. What caused it to burn on the outside?

• Friction between the air and the space ship.

• Heat was transferred from the sun to the space ship.

• Heat was transferred from the space ship to the air.

• Friction between the space ship and radiation from the sun.

Multiple Choice

What is the best shape of an object to reduce friction?

• round

• square

• rectangular

• all shapes will have the same amount of friction

Multiple Choice

What would happen if we did not have friction?

• We would be unable to stand up and walk.

• We would be able to bounce as high as we wanted.

• We would be able to float up into the clouds.

• We would not have any weight.

Multiple Choice

What type of plank should be used so that a ball will be able to move the furthest along the plank? The plank is placed flat on the ground.

• Sandy plank

• Carpeted plank

• Wooden plank

• Glass plank

Multiple Select

I want to find out if the surface of the floor affects the distance moved by a toy car. Which variable must I keep the same when carrying out the experiment?

• Type of surface used

• Mass of toy car

• The amount of initial pushing force

• Type of toy car

Multiple Choice

The diagram (picture) shows two trials of an experiment in which a spring scale was used to measure force.

Which statement is a reasonable conclusion?

• It takes more force to pull a load with more mass.

• It takes less force to move a load with more mass.

• The force needed to move a heavier load is the same as the force needed to move a lighter load.

• The mass of the marbles changes the mass of the dictionary.

Elastic Spring Force

• A material is elastic if it is able to return to its original shape after a force applied on it is removed.

• When we pull a spring and then let go of it, it returns to its original shape. The spring is elastic.

• When we pull or push a spring, it gets stretched or compressed.

• Elastic spring force is exerted by the stretched or compressed spring.

Elastic Spring Force

•Greater elastic spring force is exerted by the spring that is stretched or compressed more.

•When a greater force is applied on a spring, the extension of the spring increases.

Elastic Spring Force

Elastic Spring Force

How would a graph showing the relationship between the elastic spring force and the extensions of the springs look like?

Elastic Spring Force

​This graph shows the relationship between the elastic spring force and the extensions of the springs.

​The three springs X, Y and Z are of the same total length (4cm) when hung. However, the total mass attached to each spring is different.
Spring X is holding three identical blocks, Spring Y is holding two identical blocks, and Spring Z is holding one block. This shows that the stiffness of the springs are different. Spring X is the stiffest spring, followed by Spring Y, then lastly spring Z is the least stiff spring.

Open Ended

A type of material is used to wrap the front and back bumpers of a bumper car. What property does this material have so that it can prevent the car from damage?

Elastic Spring Force

Elastic Spring Force

Elastic Spring Force

Elastic Spring Force

A jack in the box toy has a compressed spring attached to the puppet which exerts an elastic spring force on the puppet, and the puppet exerts a push force against the lid of the box.

As the handle is turned more, the spring is compressed more and thus there is more elastic spring force exerted upon the puppet, until the push force is greater than the gravitational force acting on the lid and the puppet jumps out.

Multiple Choice

Which of the following statements about elastic spring force is false?

• Elastic spring force is exerted by a spring when the spring is stretched or compressed.

• When a force is applied on a spring, the spring extends or becomes longer.

• Elastic spring force allows a stretched spring to return to its original strength even if the spring is stretched beyond the limit.

Multiple Choice

A rubber band keeps a newspaper tightly rolled because it

• exerts its weight

• exerts elastic force

• exerts gravitational force

• exerts magnetic force

Multiple Select

Elastic spring force is the force exerted by a spring when we try to extend the spring.

• True

• False

Gravitational Force

•Gravitational force (Gravity) is the force of attraction between objects.

•It can act from a distance.

•It pulls all objects towards the centre of the Earth.

•This prevents us from floating in the air.

Gravitational Force

• It causes objects to fall downwards.

• It is harder to climb up a hill as the movement is in the opposite direction of gravitational force.

• It is easier to go down a slope as the movement is in the same direction as gravitational force.

Weight

•An object has weight due to the gravitational force acting on it.

•The further the object is from the Earth, the smaller the gravitational force acting on the object. This causes the weight of the object to decrease.

•The Earth exerts a stronger gravitational force than the Moon. Hence, an object will have more weight on the Earth than on the Moon.

•We use a spring balance to measure the weight of an object.

Weight

Weight

Multiple Select

What is effecting the amount of gravitational force?

• The speed

• The distance

• The time

• The mass

Multiple Choice

The natural force that pulls the objects toward each other called ...

• Gravity

• Light

• Space

Multiple Choice

Does the gravity really pull down?

• yes, it pull us down

• no, it pull us to the center of Earth

• yes, it push out us of the Earth

Multiple Choice

A force of attraction or pull between any two objects is called ___.

• weight

• friction

• magnetism

• gravity

Multiple Choice

Earth's tides are caused by the ___ gravitational force.

• moon's

• sun's

• planets'

• space station's

Multiple Choice

A measure of the force of gravity on an object is _____.

• mass

• weight

• gravity

• orbit

Multiple Choice

The friction between the air and a moving object is called _____.

• weight

• evidence

• gravity

• air resistance

Multiple Choice

Objects with more mass have _____ gravitational force.

• less

• more

• the same amount of

Multiple Choice

Which BEST describes the direction that gravity pulls objects?

• away from the sun

• away from Earth

• towards the center of the Earth

• to the floor

Magnetic Force

•Like gravitational force, magnetic force can act from a distance.

•It is the pulling or pushing force exerted by a magnet.

•A magnet can repel or push away another magnet when the like poles of both magnets are brought together.

•A magnet can also attract or pull another magnet towards itself when the unlike poles of both magnets are brought together.

Magnetic Force

•A magnet can attract objects that are made of magnetic materials.

•Iron and steel are examples of magnetic materials.

•

Magnetic force is able to pass through non-magnetic materials such as paper and glass.

Magnetic Force

Multiple Choice

Where is the force of attraction the strongest on a magnet?

• at the poles
• in the middle
• above the magnet
• below the magnet

Multiple Choice

Every magnet has a:

• East and West pole

• North and South pole

• East and South pole

• North and West pole

• Chicago and Saint pole

Multiple Choice

The picture is an example of an:

• Electric circuit
• Electromagnet
• Electric nail
• Electric power cell

Multiple Choice

The entire region surrounding a magnet is known as the:

• Magnetic Domain

• Lodestone

• A Compass

• Magnetic Field

Multiple Choice

Which metal can be attracted to magnets?

• Copper

• Aluminum

• Iron

• Gold

Multiple Choice

What happens if you hold the south pole of one magnet close to the north pole of another magnet?

• They will attract each other

• They will repel each other

• They will grow very hot

• Nothing will happen

Multiple Choice

Magnetism is a type of ____________

• force
• book
• plant
• animal

Multiple Select

How could I increase the strength of my electromagnet?

• More Batteries

• Smaller paper clips

• More loops of copper wire

• Larger Nail

Multiple Select

Select all the examples of an electromagnet.

• Speaker

• Motor

• Hard Drive

• Junkyard Magnet

• Refrigerator Magnet