Tag: the turning of couple

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Questions Related to the turning of 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 force the turning of couple couple turning effect of force

Two small kids weighing 10 kg and 15 kg are trying to balance a seesaw of total length 5m, with the fulcrum at the centre. If one of the kids is sitting at an end, where should the other sit?

  1. $2.5 m$

  2. $1 m$

  3. $1.7 m$

  4. $2 m$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

For a seesaw to balance, the torque on both sides must be equal. Let the fulcrum be at 0. One kid (10 kg) is at 2.5 m from the center. The other kid (15 kg) must be at distance x such that 10 * 2.5 = 15 * x. Solving for x gives 25 / 15 = 1.666... m, which is approximately 1.7 m.

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

 If principle of moments for any object holds, then object is in state of

  1. inertia

  2. equilibrium

  3. suspension

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

If principle of moments hold good, then the net torque about a given point is zero (usually CM or the pivoted point is zero). Hence the object does not rotate and is said to be in equilibrium

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

A uniform dice of mass $10kg$ radius $1m$ is placed on a rought horizontal surface. The coefficient of friction between the disc and the surface is $0.2$. A horizontal time varying force is applied on the centre of the disc whose variation with time is shown in graph.
List-I                                                         List-IIDisc rolls without slipping                   at $t=7s$Disc rolls with slipping                       at $t=3s$  Disc starts slipping at                         at $t=4s$Friction force is $10N$ at              None

  1. $A-p,q;B-p;C-r;Dq$

  2. $A-p,r;B-s;C-s,p;D-q$

  3. $A-q,r;B-p;C-s;D-q$

  4. $A-p,q,r;B-q;r;C-s;p;D-p,q,r,s$
Reveal answer Fill a bubble to check yourself
C Correct answer
Multiple choice physics turning on a pivot the turning of couple couple turning effect of force the turning effect of a force moment of force or torque

When slightly different weights are placed on the two pans of a beam balance, the beam comes to rest at an angle with the horizontal. The beam is supported at a single point P by a pivot. Then which of the following statement(s) is/are true ?

  1. The net torque about P due to the two weights is nonzero at the equilibrium position.

  2. The whole system does not continue to rotate about P because it has a large moment of inertia.

  3. The centre of mass of the system lies below P.

  4. The centre of mass of the system lies above P.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The whole system does not continue to rotate about P because the moment is balanced. Thus option B is wrong. And the center of mass of the system lies at pivot point P. Thus option C and D are wrong. As the force applied at the two points of suspension is different $\tau$ is different.