Tag: physics

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Questions Related to physics

Multiple choice physics friction advantages and disadvantages of friction merits and demerits of friction and methods to reduce it friction: a necessary evil

The efficiency of machine is reduced due to friction.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Yes, the statement is true.

Friction introduces losses and decreases efficiency since friction generates heat which is an energy that should be converted in movement. That energy in the form of heat is a loss. Also friction increases increases the wear and tear of a machine thereby decreasing its efficiency.

Multiple choice physics friction advantages and disadvantages of friction merits and demerits of friction and methods to reduce it friction: a necessary evil

A coin flicked across a table will stop, because :

  1. It is heavy

  2. No force is acting on it

  3. Earth attracts the coin

  4. Table exerts a frictional force
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

According to the first law of motion a body will remain in the state of rest or of uniform motion until or unless compelled by an external force.

In this case the coin will stop because an external force is exerted in the form of frictional force by the table that opposes the motion of the flicked coin.

Hence, correct answer is option $D$

Multiple choice physics friction advantages and disadvantages of friction merits and demerits of friction and methods to reduce it friction: a necessary evil

The application of decreasing friction includes :

  1. Ball bearing used in moving parts of a machine

  2. The streamlined shape of an aircraft

  3. The layer of air between the hull of a hovecraft.

  4. None of these.
Reveal answer Fill a bubble to check yourself
A,B,C Correct answer
Explanation

The application of decreasing friction is
(i) Ball bearings used in moving parts of a machine.
(ii) The stream lines shape of an aircraft.
(iii) The layer of air between the hull of a hovecraft.

Multiple choice physics friction advantages and disadvantages of friction merits and demerits of friction and methods to reduce it friction: a necessary evil

Which of the following are done to increase  friction?

  1. Making groove in the shoes

  2. polishing rough surface

  3. using ball bearing in wheels

  4. Creating an air cushion
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Soles of shoes are grooved because the grooves increases the friction and gives the good grip to the person while walking with shoes

Multiple choice physics upthrust in fluids, archimedes' principle and floatation upthrust is equal to the weight of displaced liquid pressure in fluids buoyancy

A bob's weight is measured by a spring balance. Its volume is $10 cm^3$. In vacuum it measures $80 g$. What does it weigh in water?

  1. $70 g$
  2. $80 g$
  3. $90 g$
  4. $76 g$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Weight of bob $= 80g/1000 N$ where $g$ is acceleration due to gravity

Weight of water displaced $= 10\times1\times g/1000 = 10g/1000 N$
Apparent weight$ = 80g/1000 - 10g/1000 = 70g/1000 N$
Weight measured $= 70/1000kg = 70 g$

Multiple choice physics upthrust in fluids, archimedes' principle and floatation upthrust is equal to the weight of displaced liquid pressure in fluids buoyancy

A ship has volume of $1,50,000 m^3$. It submerges $10\%$ in water. Upthrust felt by it equals

  1. $15 \times 10^6 N$
  2. $15 \times 10^7 N$
  3. $15 \times 10^8 N$
  4. $15 \times 10^5 N$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Volume submerged$ = 15,000 m^3 $

Upthrust $= 15000m^3 \times 1000 kg/m^3 \times 10 m/s^2$
$=15 \times 10^7 N$

Multiple choice physics upthrust in fluids, archimedes' principle and floatation upthrust is equal to the weight of displaced liquid pressure in fluids buoyancy

Consider a cylinder of height $h$ and Cross sectional area $A$ completely submerged in a fluid of density $\rho$. What is upthrust?

  1. $Ah\rho g$
  2. $Ah\rho /g$
  3. $A\rho g$
  4. $Ah^2 \rho g$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Upthrust = weight of fluid displaced

= Vol of fluid displaced x density of fluid x acc. due to gravity
$=Ah\rho g$

Multiple choice physics upthrust in fluids, archimedes' principle and floatation upthrust is equal to the weight of displaced liquid pressure in fluids buoyancy

An object having relative density 0.56 is dropped in water. Will it float or sink in water?

  1. Sink

  2. Float

  3. Depends on the density of water

  4. Unsure
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Explanation: the relative density of water is 1 and that of the object is less than 1. Thus the upthrust experienced by the object will be more than the weight of the object making it float on the surface of water.

Multiple choice physics upthrust in fluids, archimedes' principle and floatation upthrust is equal to the weight of displaced liquid pressure in fluids buoyancy

A body of density equal to density of fluid is sinking at speed of $1 m/s$ at $t=0$. What is distance covered by object in $1s$? 

  1. $0.5m$
  2. $1m$
  3. $0.75m$
  4. $0.875m$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Upthrust = weight of the body since density of body equals density of fluid

Hence, Net force $= 0$ and acceleration$ = 0$
Distance = speed x time$ = 1m$