FORCE AND PRESSURE class 8

FORCE

Q.1. Define the term force. What are its characteristics?
Ans. In science, a push or a pull on an object is called a force. The force always has a measure of its strength or magnitude and direction in which it is applied. So, Force is a vector quantity. The S.I. unit of Force is N (Newton).
Q.2. Forces are due to an Interaction. Justify. 
Ans. At least two objects must interact for a force to come into play. This means whenever a force is applied on an object, three things can be easily observed:
Ø agent exerting the force
Ø the object on which it acts
Ø the effect of the force                                                        


Q.3.  What do we mean by Net force? What are the rules for calculating net force?
Ans. The sum of all the forces acting on an object is called ‘Net force’.
                FNET =  F1 +F2+.......+FN
Rules for calculating net force :
}  If two forces applied on an object in the same direction, the net force acting on it is the addition of the applied forces.

}  If the two forces act in the opposite directions on an object, the net force acting on it is the difference between the two applied forces. 


Q.4. What are balanced and unbalanced forces?
Ans. If the sum of the forces acting on an object is zero (means the net force on an object is Zero), then such forces are said to be balanced  forces.
If the sum of the forces acting on an object is non-zero (means the net force on an object is non-Zero), then such forces are said to be unbalanced  forces.


Q.5. Calculate the Net Force.
Ans. As forces are acting from both directions. The net force will be 0 N to the right {(2N + 3N) + (-5N)}= 0 N). So, the box will not move.


Q.6. Calculate the Net Force.
Ans. As forces are acting from both directions. The net force will be [(15N +17N + 5N) - (25N + 8N)] = 37 - 33 = 4N towards west direction as sum of the forces applied towards west is more than sum of forces applied towards east.

 Q.6. Calculate the Net Force.
Ans. As all forces are acting in the same direction, the net force will be 400N to the right (200N + 100N +100 N= 400N). So, box will move to the right.

Q.7. What are the various effects of force?
Ans. i) Force may make an object move from rest or at rest if moving. 

          ii) Force may change the speed of an object if it is moving.

         iii) Force may change the direction of motion of an object.

         iv) Force can Change the Shape of an Object.


Q.8. What are the types of forces?
Ans.



















Q.9. Write a short note on each:
         i) Muscular force: The force resulting due to the action of muscles is known as the muscular                                              force.

        ii) Friction: The force which opposes the motion of an object on the surface of another object is                              called force of friction.

       iii) Magnetic force: The force observed between two magnets or between a magnet and a                                                      magnetic material is called magnetic force.


       iv) Electrostatic force: The force exerted by a charged body on another charged or uncharged                                                  body is known as electrostatic force. 


       v) Gravitational force: Gravitational force is the force of attraction with which every body in                                                   the universe attracts every other object. 

  



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