revision for primary 5

Question one:
Complete the following:
1- The friction force can be observed between ……… and ……… .


2- The friction force affects in ……… direction of ……… .


3- The ……… force exists between two forces.


4- When the cube slides down on the wooden board, the friction force is ……… .


5- The friction force between two surfaces made of glass is ……… than friction between glass and metal.


6- The friction causes ……… for parts of machines.


7- The temperature rises inside machines is due to ……… .


8- Friction forces can be decreased by using ……… and ……… .


9- Technicians use ……… to decrease friction in wheels.


10- The smooth surface of balls in ball bearing makes the friction force ……… .






Question two:
Give reasons for:
1- The rubber ball stops after time on moving on the ground.


2- The friction force decreases the speed.


3- The internal parts of machines are damaged.


4- Some machines become hot on using them.


5- Using of lubricants and oil in some machines.


6- The friction between balls in ball bearing is almost non exist.


7- The friction forces are not constant.


Question three:
What is meant by:
1- Friction force:


2- Ball bearing:


Question four:
Write two disadvantages of friction force.
Question five:
Write two methods to decrease friction force.


Question six:
Explain why we need to push bicycle tires to move





Question one:
Complete the following:
1- The friction force can be observed between ……… and ……… .
bicycle tire – ground



2- The friction force affects in ……… direction of ……… .
opposite – movement



3- The ……… force exists between two forces.
friction



4- When the cube slides down on the wooden board, the friction force is ……… .
small



5- The friction force between two surfaces made of glass is ……… than friction between glass and metal.
smaller



6- The friction causes ……… for parts of machines.
damage



7- The temperature rises inside machines is due to ……… .
friction



8- Friction forces can be decreased by using ……… and ……… .
lubricants – oil



9- Technicians use ……… to decrease friction in wheels.
ball bearing



10- The smooth surface of balls in ball bearing makes the friction force ……… .
Question two:
Give reasons for:
1- The rubber ball stops after time on moving on the ground.
Due to friction force.




2- The friction force decreases the speed.
Because it affects in opposite direction of movement.



3- The internal parts of machines are damaged.
Due to friction force.



4- Some machines become hot on using them.
Due to friction force.



5- Using of lubricants and oil in some machines.
To decrease the friction force.



6- The friction between balls in ball bearing is almost non exist.
Due to their smooth surfaces.



7- The friction forces are not constant.
Because they change by change of the material of surface.







Question three:
What is meant by:
1- Friction force:
The force that affects in opposite direction of movement.


2- Ball bearing:
Group of balls exists between two surfaces to decrease friction.



Question four:
Write two disadvantages of friction force.
1- Damage of internal parts of machines
Question five:
Write two methods to decrease friction force.
1- Using lubricants and oil.
2- Using ball bearing.


Question six:
Explain why we need to push bicycle tyres to move.
Because there is a friction force between tyres and the ground