Question one:
Complete the following:
1- Friction forces can be observed in ……… , ……… and ……… .
solids – liquids – air
2- The friction forces can be observed in air only when the objects move ……… .
so fast
3- Air crafts, rockets and trains are having ……… shape to overcome ……… force.
Streamline – friction
4- The friction in air is known as ……… while friction in water is known as ………
air resistance – water resistance
5- There is a ……… relation between friction and ……… of a moving object.
direct – surface
6- The car is said to be moving by constant velocity when ……… force equals ……… force.
motion – friction
7- The friction force affects in ……… direction of movement.
opposite
8- As the body moves fast in water, its resistance ……… .
increases
9- The fish has ……… shape to decrease ……… .
streamline – friction
10- Friction prevents people from ……… during walking.
slipping down
11- Lightening of a match depends on ……… force.
friction
12- By friction force cars can move ……… .
forward
13- The car tyres contain ……… to increase friction.
grooves
Question two:
Write three advantages of friction.
1- Car can move forward.
2- People can walk.
3- Lightening of a match.
Question three:
Give reasons for:
1- Rockets and aircrafts have streamlined shape.
To decrease friction force with air.
2- The fish has streamline shape.
To decrease friction force with water.
3- People can walk on the ground.
Due to the presence of friction force.
4- Fast boats are designed in small surface.
To decrease friction force with water.
5- Friction can be observed only in fast objects in air.
Because air has small mass.
Question four:
Comparison:
Compare between air resistance and water resistance.
Amount of resistance is due to friction through air
Observed by fast objects
Amount of friction force on moving through water
Observed by moving objects
Question five:
"Friction is one of the basic forces". Explain.
Because it is used in many objects to move and change speed or direction.