Questions Related to couple

Multiple choice physics forces - vectors and moments the turning of couple couple rotational motion of a rigid body and moment of inertia turning effect of force

State whether true or false.
A couple can never be replaced by a single force.

  1. True

  2. False

Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A couple is defined as a pair of two equal and opposite parallel forces acting along two different lines. A couple can produce roatation in the body but not the translational motion. A single force can produce translation motion in the body. Thus the given statement is true that a couple can never be replaced by a single force.

Multiple choice physics forces - vectors and moments the turning of couple couple rotational motion of a rigid body and moment of inertia turning effect of force

State whether true or false.
Only a couple can produce pure rotation in a body.

  1. True

  2. False

Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A couple is defined as a pair of two equal and opposite parallel forces acting along two different lines. Since net force acting on the body is zero, so the body is in translatory equilibrium. A couple produces torque which rotates the body. Thus the given statement is true that only a couple can produce pure rotation in a body.

Multiple choice physics forces - vectors and moments the turning of couple couple rotational motion of a rigid body and moment of inertia turning effect of force

While opening a tap with two fingers, the forces applied by the fingers are:

  1. equal in magnitude

  2. parallel to each other

  3. opposite in direction

  4. all the above

Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

A couple has to be applied to the tap in order to open it. A couple is the combination of two equal and opposite parallel forces acting at different axes. Thus option D is correct.

Multiple choice physics forces - vectors and moments the turning of couple couple rotational motion of a rigid body and moment of inertia turning effect of force

$ML^2T^{-2}$ is the dimensional formula for

  1. moment of inertia

  2. pressure

  3. elasticity

  4. couple acting on a body

Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

$\left[ MOI \right] =\left[ M{ R }^{ 2 } \right] =\left[ { M }^{ 1 }{ L }^{ 2 }{ T }^{ 0 } \right] \ \left[ Pressure \right] =\left[ N/{ M }^{ 2 } \right] =\left[ { M }^{ 1 }{ L }^{ -1 }{ T }^{ -2 } \right] \ \left[ Couple \right] =\left[ N.{ M } \right] =\left[ { M }^{ 1 }{ L }^{ 2 }{ T }^{ -2 } \right] $

Multiple choice physics forces - vectors and moments the turning of couple couple rotational motion of a rigid body and moment of inertia turning effect of force

An automobile engine develops $100$ $kW$ when rotating at a speed of $1800\ rev/min$. The torque it delivers is

  1. $3.33\ N-m$

  2. $200\ N-m$

  3. $530.5\ N-m$

  4. $2487\ N-m$

Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

$Power\quad P=100kW\quad =100000W\ w=1800\times \cfrac { 2\pi  }{ 60 } \quad rad/s\ \quad =60\pi \quad rad/s\ P=torque\times w\ torque=530.5\quad Nm$

Multiple choice physics turning on a pivot the turning effect of a force moment of force or torque turning effect of force couple

While opening a tap with two fingers, the forces applied are  

  1. equal in magnitude

  2. parallel to each other

  3. opposite in direction

  4. All of the above

Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

While opening a tap with two fingers, a couple should be applied which is defined as a pair of parallel equal forces acting in opposite direction about two different axis.

Multiple choice physics turning on a pivot the turning effect of a force moment of force or torque turning effect of force couple

On applying a constant torque on a body-

  1. linear velocity increases

  2. angular velocity changes

  3. it will rotate with constant angular velocity

  4. it will move with constant velocity

Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A constant torque applied to a rigid body results in constant angular acceleration, which causes the angular velocity to change over time.

Multiple choice physics turning on a pivot the turning effect of a force moment of force or torque turning effect of force couple

It becomes easier to open or close a door turning about its hinges if the force is applied at the:

  1. Two third of the door

  2. Free edge of the door

  3. Middle of the door

  4. Point near the hinges

Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Torque acting about any point O         $\tau _o = rF$                 for $sin\theta = 1$

where $r$ is the distance of the application of force from point O.
As  $r$ is maximum when a force is applied at the free end of the door, thus less amount of force is required to produce the same torque. Hence it is easier to open or close the door if force is applied at its free end.