What does the friction exerted by fluids on an object depend on?
P) Size of the object
Q) Speed of the object
R) Shape of the object
i. Only P
ii. Only P and Q
iii. Only Q and R
iv. All P, Q and R
Answers
Answer:
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Page No 146:
Question 1:
A force can move a stationary object. If force is applied to a stationary object, does it always move?
ANSWER:
No, it is not necessary that the stationary object will move always when a force is applied. If there is a friction force between the object and the ground then the friction force will oppose the motion of the object. Hence, the stationary object will move only if the applied force is greater than the friction force between the object and the ground.
Page No 146:
Question 2:
Two equal forces act on an object. Is this information enough to say which way the object will move? Give reasons.
ANSWER:
No, this information is not enough. Two equal forces may or may not cause an object to move. If both the forces are acting on the same side of the object and are large enough to overcome the friction force between the object and the ground, then the object will move. If both the forces are acting on the object from the opposite directions then the object will not move as the net force on the object will become zero.
Hence, the direction of the force and value of the friction force must be defined in order to determine the movement of the object.
Page No 146:
Question 3:
Name the force that acts on all bodies on the earth at all times.
ANSWER:
Gravitational force is the force which acts all the time on all the bodies present on the earth. It's equal to the weight of a body and always directed towards the center of the earth.
Page No 146:
Question 4:
Name a force that always opposes motion.
ANSWER:
The friction force is the force which always opposes the motion. Friction force acts due to irregularities and roughness of the surface.
Page No 146:
Question 5:
Can a force act on an object even when it is not in contact with the object? Give examples.
ANSWER:
Magnetic force is the force which can act on an object without making any contact with the objects. Example: Force exerted by a magnet on another magnet.
Page No 151:
Question 1:
A force acts perpendicular to a given surface. What is the quantity 'force per unit area' known as?
ANSWER:
The quantity 'force per unit area' is known as 'pressure'.
Page No 151:
Question 2:
How is pressure related to the area over which a force acts?
ANSWER:
The pressure is defined as the force per unit area. So, the pressure is indirectly proportional to the area over which the force acts.
Answer:
iv) All
Explanation:
Size would increase it mass, increasing friction.
speed would also increase friction.
with a wider shape, the area in contact will be more, increasing friction.
thank you.