FORCES REVISON

FORCES REVISON

Multiple Select

Air resistance can cause an object to

• increase speed

• decrease speed

• change directon

• all of the above

Multiple Choice

Are the forces balanced or unbalanced?

• balanced to the right

• unbalanced to the right

• balanced to the left

• unbalanced to the left

Multiple Choice

Calculate the resultant force

• 50 N to the right

• 50 N to the left

• 60 N to the right

• 60 N to the left

Multiple Choice

calculate the resultant force.

• 20N to the right

• 20N to the left

• 0 N to the right

• 0 N to the left

• 0 N

Multiple Choice

Calculate the resultant force

• 300N to the right

• 300N to the left

• 590N to the right

• 590N to the left

Open Ended

Give two examples from everyday life that uses friction.

Open Ended

Suggest ways to reduce friction

Multiple Choice

Stretching

• When a material or object is squashed

• Something that returns to its original shape and size after being stretched or squashed

• When a material of object is pulled

• Change in size and/or shape when a force is applied

Multiple Choice

Compression

• When a material or object is squashed

• Something that returns to its original shape and size after being stretched or squashed

• When a material of object is pulled

• Change in size and/or shape when a force is applied

Multiple Choice

Deformation

• When a material or object is squashed

• Something that returns to its original shape and size after being stretched or squashed

• When a material of object is pulled

• Change in size and/or shape when a force is applied

Multiple Choice

Elastic

• When a material or object is squashed

• Something that returns to its original shape and size after being stretched or squashed

• When a material of object is pulled

• Change in size and/or shape when a force is applied

Hooke's law

• The extension of a material or a spring is its increase in length when pulled.

• Hooke’s Law says that the extension of an elastic object is directly proportional to the force applied to it.

Investigating Hooke’s Law

• Set up the apparatus as in the diagram

• Add a 10 g mass to the holder and record the spring length.

• Add another 10 g mass and record the new spring length.

• Take away the previous spring length from the new length to calculate the extension (the difference).

• Repeat by adding 10 g masses until 100 g is reached.

Multiple Choice

What is the independent variable in the above investigation?

• mass

• extension

• stretched length

• spring

Multiple Choice

What is the dependent variable in the above investigation?

• mass

• extension

• stretched length

• spring

Multiple Choice

What is the control factor in the above investigation?

• mass

• extension

• stretched length

• spring

Turning forces

• Forces can make objects turn if there is a fulcrum

• The turning forces around a fulcrum are called moments

• Moment =              Force x distance

  
  

• Moment  =      F     x      d

  
  

•   The units for moment are Nm, Ncm

Law of moments

For a balanced see-saw, the anticlockwise moments are equal and opposite to clockwise moments

Multiple Choice

In the given picture, John is 0.5m from the pivot, Peter is 1m from the pivot? Is it in equilibrium

• Yes, both clockwise and anticlockwise moments are equal

• No, anticlockwise moment is greater which is 350Nm

• No, clockwise moment is greater which is 500Nm

• No, anticlockwise moment is greater which is 700Nm

Multiple Choice

In the given picture, John is 1m from the pivot, Peter is 1.4m from the pivot? Is it in equilibrium

• Yes, both the clockwise and anticlockwise moments are balanced.

• No, clockwise moment is greater which is 700Nm

• No, anticlockwise moment is greater which is 700Nm

• No, anticlockwise moment is greater which is 980Nm

Multiple Choice

In the given picture, John is 0.4m from the pivot, Peter is 0.56m from the pivot. Is it balanced?

• Yes, both clockwise and anticlockwise moments are equal

• No, clockwise moment is greater which is 200Nm

• No, anticlockwise moment is greater which is 392Nm

• No, clockwise moment is greater which is 392Nm

Multiple Choice

A counterweight is used to make a crane balance.

How far away must the 5,000N load be in order for the crane to be balanced?

• 0.16 m

• 0.15 m

• 6 m

• 1.5 m

Multiple Choice

A counterweight is used to make a crane balance. If the load is increased to 10,000N how far away should it be?

• 1 m

• 3 m

• 2 m

• 4 m

Multiple Choice

Fluid

• The pressure caused by the weight of the air above the surface

• The upward force that a liquid or gas exerts on a body floating in it

• A substance with no fixed shape, a gas or a liquid

• The ratio of force to surface area and how it causes stress in solids

Multiple Choice

Pressure

• The pressure caused by the weight of the air above the surface

• The upward force that a liquid or gas exerts on a body floating in it

• A substance with no fixed shape, a gas or a liquid

• The ratio of force to surface area and how it causes stress in solids

Multiple Choice

Upthrust

• The pressure caused by the weight of the air above the surface

• The upward force that a liquid or gas exerts on a body floating in it

• A substance with no fixed shape, a gas or a liquid

• The ratio of force to surface area and how it causes stress in solids

Multiple Choice

Atmospheric Pressure

• The pressure caused by the weight of the air above the surface

• The upward force that a liquid or gas exerts on a body floating in it

• A substance with no fixed shape, a gas or a liquid

• The ratio of force to surface area and how it causes stress in solids

Liquid pressure

• The pressure in a liquid depends on the height

• The sea bed experiences a greater pressure

• This is because there are more particles above that push down on the object

Upthrust

• Liquid pressure is exerted on the surface of an object in a liquid. This pressure causes upthrust.

• An object placed in a liquid will begin to sink.

• As it sinks, the liquid pressure on it increases and so the upthrust increases.

• For a floating object, the upthrust is equal and opposite to the object’s weight.

• An object will continue to sink if its weight is greater than the maximum upthrust.

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Multiple Select

In the given picture the raft floats because

• upthrust is greater than weight

• upthrust is equal to weight

• upthrust is smaller than weight

• weight is greater than upthrust

Multiple Choice

In the given picture at the bottom of which container is the pressure greatest?

• A

• B

• C

• all of them have the same pressure

• Impossible to tell

Gas pressure

• gas particles are always moving and colliding.

• When they hit into you they cause a force. This causes a pressure on you. 

  
  

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Gas pressure

• This pressure is the same for everyone and it is the same on every part of your body.

• 
  

• 
  

Factors affecting gas pressure

• Quantity

• Number of gas particles

Factors affecting gas pressure

• Temperature

• How fast they move

Multiple Choice

The higher you go up a mountain the ____________ pressure there is.

• More

• less

• same

• impossible to say

Pressure in solids

• force (N)/area (m²).

• The unit of pressure is N/m²

Multiple Choice

A force of 500 N acts over an area of 10 m². Calculate the pressure.

• 5000 N/m²

• 50 N/m²

• 50 m²/N

• 50 N/cm²

Multiple Choice

A girl has a weight of 450 N and her feet have a total area of 300 cm². Calculate the pressure her feet put on the ground.

• 1.5 N/m²

• 135000 N/m²

• 135000 m²/N

• 1.5 N/cm²

Multiple Choice

A hammer hits a nail with a force of 50 N into some wood. The area of the point of the nail is 0.02 cm². What is the pressure the nail puts on the wood?

• 1 N/m²

• 2500 N/m²

• 2500 N/cm²

• 1 N/cm²

Multiple Choice

A car of weight 6,400 N has four wheels. Each wheel has an area of 80 cm² touching the road. Find the pressure the car puts on the ground.

• 80 N/m²

• 80 N/cm²

• 20 N/m²

• 20 N/cm²

Multiple Choice

A student uses a glue stick with an area of 4 cm², putting a pressure of 0.5 N/m² on her book. Calculate the force she puts on the glue stick

• 2 N/m²

• 2 N

• 8 N/cm²

• 0.125 N/cm²