Tag: fluid friction

Questions Related to fluid friction

Mr. Verma (50 kg) and Mr. mathur (60 kg) are sitting at the two extreames of 4 m long boat (40 kg) standing still in water. to discuss a mechanics problem, they come the middle of the boat . neglecting friction with water, how far does the boat move in the water during the process?

physics dynamics - explaining motion air resistance fluid friction moving through fluids

  1. $1.33 m$

  2. $2 m$

  3. $10 m$

  4. $1 m$

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Correct Option: A

Smooth surface produces ----- friction than a rough surface.

physics dynamics - explaining motion air resistance fluid friction moving through fluids

  1. Less

  2. More

  3. Constant

  4. None of these above

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Correct Option: A
Explanation:

[A]  less

As the coefficient of friction $( \mu)$ is less for smooth surfaces 
so they produce less friction than rough surface.

The arrow with a pointed tip can move faster in air than that of with a blunt tip.

physics dynamics - explaining motion air resistance fluid friction moving through fluids

  1. True

  2. False

  3. Ambiguous

  4. Data insufficient

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Correct Option: A
Explanation:

A pointed tip is more sharper than a blunt tip. So the air resistance for the pointed tip is less than that of the blunt tip. Since the air resistance opposes the motion, so the pointed can tip move faster than that of blunt tip. Thus, the given statement is true.

State whether the given statement is true or false:

Fluid friction is more than solid friction.

physics dynamics - explaining motion air resistance fluid friction moving through fluids

  1. True

  2. False

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Correct Option: B
Explanation:

Static friction is the force that is the greatest. This is because it opposes motion the strongest between the various types of friction. Friction is greatest in the absent of lubrication,and since there is presence of fluid lubricant in fluid friction it has less friction as compared to solid friction,and in solid friction there is no presence of any lubricant.Hence the given statement is false.

A man of mass $m$ walks from end $A$ to the other end $B$ of a boat of mass $M$ and length $l$. The coefficient of friction between the man and the boat is $ \mu $ and neglect any resistive force between the boat and the water.

physics dynamics - explaining motion air resistance fluid friction moving through fluids

  1. If the man runs at his maximum acceleration, the acceleration of the boat is $ (m/M)g $.

  2. The maximum time take by the men to reach the other end of the boat is $ \sqrt { \dfrac { 2Ml }{ (M+m)\mu g } } $.

  3. If the man runs at his maximum acceleration, the acceleration of the boat is $ \dfrac { m }{ m+M } \mu g $.

  4. The minimum time take by the men to reach the other end of the boat is $ \sqrt { \dfrac { 2ml }{ (M+m)\mu g } } $.

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Correct Option: A,B