FORCE and Pressure (Part - 1)
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).
- For example: 40N towards EAST. Here, 40N is called magnitude and East is the direction of force applied.
Q.2. Write Push or Pull for following actions:
Ans.
Q.3. In the following situations
identify the agent exerting the force and the object on which it acts.
i) Taking out paste from a
toothpaste tube.
} We use our muscular force to take out paste from a toothpaste tube. The muscular force is exerted on the toothpaste tube (the object) by our fingers (agent) .
ii) A load suspended from a spring
while its other end is on a hook fixed to a wall.
} The suspended load (agent) exerts a force on the spring and pushes the spring (the object) downwards.
iii) An athlete making a high jump
to clear the bar at a certain height
} An athlete (agent) pushes the ground (the object) with his feet.
Q.4. 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.5. 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’.
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.6. 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.7. 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.8. 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.9. 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.10. What are the various effects of force?
Q.9. Calculate the Net Force.
Q.10. What are the various effects of force?
Ans. i) Force may make an object move from rest or at rest if moving :
- Kicking a ball that is stationary brings it from rest to motion.
- Catching a ball brings it from motion to rest.
ii) Force may change the speed of an object if it is moving:
- If someone kicks a moving ball in the same direction, it's speed increases.
- If someone pulls a moving bicycle from behind, it's speed decreases.
iii) Force may change the direction of motion of an object:
- In cricket, a batsman plays his or her shot by applying a force on the ball with the bat, it's direction changes.
- In football, when a player passes the football to another player, it's direction changes.
iv) Force can Change the Shape of an Object:
- When we apply a force on an inflated balloon by pressing it between our palms, it's shape changes.
- Shape of a ball of dough changes when it is rolled to make a chapati.
