8.2 EFFECT OF FORCE (PRESSURE)

8.2 EFFECT OF FORCE (PRESSURE)

by KASMAWATI Moe

​Watch this video (4 mins)

​Make sure to understand:

• ​Definition of Pressure

• Formula of Pressure​

• Unit of Pressure

Pressure

The effect of thrust on a surface depends also upon the area on which thrust acts.

Pressure is defined as force acting per unit area.

Pressure is inversely proportional to the area on which the force acts.

More is the area on which force acts less is the Pressure and vice versa

NOW THINK

WHY HEAVY VEHICLES LIKE TRUCK HAVE 8 TO 10 TYRES?

WHY A SHARP KNIFE IS BETTER THAN A BLUNT ONE?

Pressure equation

• Pressure is described as force applied per unit area.

• Pressure is measured in Pascals (Pa).

• Area is measured in m2.

• Force is measured in Newtons (N).

• If a force of 100 N is applied to an area of 10m2, the pressure would be equal to = 100 / 10.

• Pressure = 10 Pa.

Air Pressure

High vs Low

Read this slide twice: Make sure you understand what you are reading

Read this slide twice: make sure you understand what you are reading

Multiple Choice

Which type of air mass has a higher pressure?

• Humid and warm

• cold and dry

• humid and cold

• warm and dry

Multiple Choice

Which type of air mass has low pressure?

• cold and dry

• warm and humid

• cold and humid

• warm and dry

Multiple Choice

What is pressure?

• The amount of force exerted on a surface

• The surface area of an object

• The weight of an object

Multiple Choice

What is the equation used to calculate pressure?

• pressure= force/mass
• pressure =mass/volume
• pressure=area/force
• pressure=force/area

Multiple Choice

Pressure is measured in what units

• Newtons
• m/s
• Pascals
• Moles

Multiple Choice

The pressure resulting from a force of 50 N exerted over an area of 5 m² is

• 10 N
• 0.1 N
• 10 N/m²

• 0.1 Pa

Multiple Choice

What pressure will be exerted by a 10 N box that has equal sides of 2 m?

• 5 Pa

• 2.5 Pa

• 1.25 Pa

• 0.2 Pa

• 0.4 Pa

Multiple Choice

Which of the statements is true?

• The bottom of the boot exerts more pressure than the shoe as a result of an increase in surface area.
• The bottom of the shoe exerts more pressure than the boot as a result of an decrease in surface area.
• The bottom of the shoe exerts the same pressure as the bottom of the boot.

Multiple Choice

What pressure does a 4000N horse exert on the ground if each foot is 10cm²?

• 40 N/cm²
• 100 N/cm²
• 400 N/cm²
• 10 N/cm²

Multiple Choice

Army tank tracks are useful for travelling through the mud because..

• they decrease the force the vehicle exerts on the ground

• they increase the force the vehicle exerts on the ground

• they decrease the pressure the vehicle exerts on the ground

• they increase the pressure the vehicle exerts on the ground

Multiple Choice

When a diver dives deeper into the ocean, he will experience ...................... liquid pressure

• greater

• less

• no

Multiple Choice

An object will ______ if its' density is greater than the density of the fluid it is in. 

• Expand
• Shrink
• Float
• Sink

Multiple Choice

Air pressure is greatest when near Earth's surface because?

• The air molecules are farther apart.
• The air molecules are closer together.
• Air molecules collide.
• Air molecules are tightly packed.

Multiple Choice

As you climb up a mountain what happens to the air pressure?

• decreases

• increases

• stays the same

Multiple Choice

In what direction(s) does air exert pressure?

• everywhere

• no where

• there is no pressure

• downward

Multiple Choice

Where would you find the largest pressure?

• At the bottom of the ocean
• At the top of Mt Everest
• Close to ground on the Scotch oval
• In a rockpool on the Great Barrier Reef

Multiple Choice

Pressure rxerted by air on the earth's surface

• Pressure

• Atmospheric pressure

• Heat pressure

Multiple Choice

What is true about the volume of displaced fluid for an object that is completely submerged?

• The volume of displaced fluid is equal to the object’s volume.

• The volume of displaced fluid is less than the object’s volume.

• The volume of displaced fluid is greater than the object’s volume.

• The volume of displaced fluid is not related to the object’s volume.

Multiple Choice

An object will _______ if the weight of it is equal to the weight of the water in which it is in. 

• Float
• Sink
• Expand
• Shrink

Multiple Choice

A person wearing steel toe capped boots and a person wearing stilleto heels stand on a wooden floor. They both have the same weight. Which person exerts a greater pressure on the floor?

• The person wearing the boots because the boots have a larger surface area in contact with the floor

• The person with the stiletto heels because they have a larger surface area in contact with the floor

• The person wearing the boots because the boots have a smaller surface area in contact with the floor

• The person with the stiletto heels because they have a smaller surface area in contact with the floor

Multiple Choice

Look at the pressure triangle. How do we calculate the area?

• f ÷ a

• f x p

• p x f

• f ÷ p

Multiple Choice

Which of these animals would probably cause the greatest pressure on the ground?

• A fat cow with big feet
• A fat cow with small feet
•  A calf with big feet
• A calf with small feet

Multiple Choice

Army tank tracks are useful for travelling through the mud because..

• they decrease the force the vehicle exerts on the ground

• they increase the force the vehicle exerts on the ground

• they decrease the pressure the vehicle exerts on the ground

• they increase the pressure the vehicle exerts on the ground