Gravity and Friction

Gravity and Friction

Alef Lesson 114

Textbook pages 388-390

FORCE

• A force is push or pull.

• Forces are measured in the unit newton (N).

• Forces have direction and strength and is represented by arrows.

• Forces can be contact or non-contact.

Multiple Choice

Observe the picture: Push or Pull?

• Push

• Pull

Multiple Choice

Observe the picture: Push or Pull?

• Push

• Pull

Multiple Choice

Observe the picture: Push or Pull?

• Push

• Pull

Multiple Select

Gravity and friction are types of forces.

• Yes

• No

GRAVITY

• Gravity is the force of attraction between any two objects.

• 
  

  
  

• 
  

  
  

• 
  

  
  

Multiple Choice

What are the 2 objects in the video shown by Laith where force of attraction exist?

• air and ball

• earth and air

• ball and earth

GRAVITY

• Gravity is the force of attraction between any two objects.

• The force of attraction between objects depends on the mass of the objects and the distance between them.

• The force of gravity decreases as mass decreases.

• The force of gravity decreases as distance increases.

Multiple Choice

You will float outside the Earth.

• Yes

• No

FRICTION

• Friction is a force that resists the motion of objects.

• Friction exists between objects that are touching - sliding, rolling or rubbing.

• Friction depends on:

  1) the type of surface  2) the amount of force with which the surfaces are pressed together 3) the weight of an object

Multiple Choice

Which force caused the hands of Mansoor to get warm as he rubbed them?

• gravity

• friction

• magnetic force

Multiple Select

To reduce friction, applying oil between surfaces is effective.

• Yes

• No

• Maybe

AIR RESISTANCE

• Air resistance is a type of friction that occurs between objects moving through air.

Multiple Choice

Which of these will happen when there is no air resistance?

• Objects will accelerate equally.

• Friction is harmful.

• No effect.

AIR RESISTANCE

• When an object moves through a fluid (a liquid or a gas) the molecules in the fluid bump against the object, causing it to slow down.

  
  

  When the paper was placed on top of the book, the book blocked the air and reduced the drag forces acting on the paper.