E. Answer the following in short.
1. Define force. Write its Sl unit.
2. Why does a 'charged' balloon stick to a wall?
3. Why is magnetic force considered as an action-at-a-distance force?
4. Define rolling friction and give an example where rolling friction comes into play.
5. How can sliding friction be changed into rolling friction easily?
6. What is the basic principle for increasing friction?
7. Why do wrestlers rub a special substance on their hands before getting into the ring?
8. What is 'streamlining?
Answers
Answer 1=Force is a push or a pull that changes or tends to change the state of rest or uniform motion of an object or changes the direction or shape of an object. It causes objects to accelerate. SI unit is Newton.
Answer 2=When you rub a balloon against your clothes and it sticks to the wall, you are adding a surplus of electrons (negativecharges) to the surface of the balloon. ... As the two come in contact, the balloonwill stick because of the rule that opposites attract (positive to negative).
Answer 3=Magnetic force considered as an action at a distance force because; it comes into play even when the magnetand other object (like iron) are kept at adistance and not in direct contact with each other. Hence, magnetic-force isconsidered as an action- at-a-distance force.
Answer 4=When we roll an object on a surface, thefriction produced between the object and the surface is called rolling friction.Example : When we pull our large suitcases on wheels, rolling friction comes into play.
Answer 5=Sliding friction can be changed into rolling friction easily by providing wheels or ball bearings to the objects to reducefriction and facilitate easy movement.
Answer 6=The basic principle for increasing friction is by increasing the roughness of the surfaces in contact.
Answer 7=In order to prevent their hands from slipping over their opponent's body. The powder increases the friction.
Answer 8=Streamlining, in aerodynamics, the contouring of an object, such as an aircraft body, to reduce its drag, or resistance to motion through a stream of air.
Explanation:
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