Tag: dynamics - explaining motion

Questions Related to dynamics - explaining motion

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

When a running horse suddenly stops, the rider falls forwards.

physics dynamics - explaining motion concept of inertia galileo's law and inertia mass and inertia

  1. True

  2. False

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Correct Option: A
Explanation:

the statement is true and the reason is Newton's law of inertia or First law of motion. 

As body tends to be in its original state when the horse suddenly stops, the lower part of rider stops with it but upper part remains in motion. So, rider falls forward.

Galilee's law of inertia is another name for newton's (... ) law of motion.

physics dynamics - explaining motion concept of inertia galileo's law and inertia mass and inertia

  1. First

  2. Second

  3. Third

  4. Anyone of the above

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Correct Option: A
Explanation:

Galileo's law of inertia is another name for newton's First law of motion. Newton's first law states that an object will remain at rest or move at a constant speed in a straight line unless it is acted on by an unbalanced force. Inertia comes from mass. Objects with more mass have more inertia.

What is the other name of Galileo's law of falling bodies?

physics dynamics - explaining motion concept of inertia galileo's law and inertia mass and inertia

  1. Law of motion

  2. Newton's first law

  3. Newton's second law

  4. Newton's third law

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Correct Option: C
Explanation:

Galelio’s hypothesis stated,”A falling body accelerates uniformly: it picks up equal amounts of speed in equal time intervals, so that, if it falls from rest, it is moving twice as fast after two seconds as it was moving after one second, and moving three times as fast after three seconds as it was after one second.”


The term inertia was first used by

physics dynamics - explaining motion concept of inertia galileo's law and inertia mass and inertia

  1. Newton

  2. Galileo

  3. Aristotle

  4. Kepler

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Correct Option: B
Explanation:

Galileo, a premier scientist in the seventeenth century, developed the concept of inertia. Galileo reasoned that moving objects eventually stop because of a force called friction. First thing it was discovered and not invented. It was discovered and stated and proved by Sir Isaac Newton.

Hence,
option $B$ is correct answer.

Which of the following systems of units is not based on units of mass, length and time alone ?

physics dynamics - explaining motion summary of si units fundamental quantities system of units

  1. SI

  2. MKS

  3. CGS

  4. FPS

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Correct Option: A
Explanation:

SI system is based on seven fundamental units. These fundamental units are Kelvin, Second, Kilogram, Metre, Candela, Mole and Ampere.