Torque

Q. Q. A Flywheel of mass 60 kg and radius 40cm is revolving at 300 rpm then its rotational K.E. is a\rbrack 48/π^{2 } J b\rbrack 480π J c\rbrack 48/π J d\rbrack 240π^2 J

Q.

Relation between torque and angular momentum is similar to the relation between

1. force and linear momentum

2. mass and moment of inertia

3. energy and displacement

4. acceleration and velocity

Q. when earth revolve around the sun then 1 angular momentum is conserved 2 linear momentum is not conserved 3 external torque is ero 4 all of these

Q. A rectangular coil 6 cm long and 2 cm wide is placed in a magnetic field of 0.02 T. If the loop contains 200 turns and carries a current of 50 mA, the torque on the coil when its area vector is perpendicular to the field will be?

1. $2.4\times {10}^{-4}Nm$
2. 2.4 Nm
3. 0.24 Nm
4. 0.024 Nm

Q. A rectangular loop of size (3cm×5cm) having 100 turns carries current of 2 A placed in a uniform magnetic field of 5T. If angle between plane of coil and magnetic field is 37°. The torque acting on the loop is Axis of rotation is lying in the plane and perpendicular to B

Q. two equal masses are placed at a dis†an cer from each other.where does the centre of mass

Q. If F is the force acting on the particle having position vector r and τ be the torque of this force about the origin then 1) r.τ >0, and F. τ < 0 2) r.τ =0 , F.τ =0 3) r.τ =0, F.τ not equals to 0 4) r.τ not equals 0, F.τ =0

Q. A 10 metric ton drives up a hilly road of gradient 1 in 50 at a speed of 36 kmh^{-1}. If the coefficient of kinetic friction between the road and tyresis 0.2, find the power delivered by the engine (g=10ms^{-2}) (1) 12×10^4W (2) 32×10^4W (3) 22×10^4W (4) 2.2×10^4W

Q. Is magnetic force a conservativ or non-conservative force and why?

Q. a uniform meter scale can be balanced at 70cm mark when mass of 0.005kg is hung from 94cm mark 1.draw diagram of arrangement 2.find mass and meter scale

Q. 19.The value of 120 joule per second on a system that has 10 g , 100cm , 1000 second as base unit is

Q.

When forces $F_1$, $F_2$, $F_3$ are acting on a particle of mass m such that $F_2$ and $F_3$ are mutually perpendicular, then the particle remains stationary. If the force $F_1$ is now removed then the magnitude acceleration of the particle is:

1. 

2. 

3. 

4. 

Q.

Which of the following quantity has the unit of newton-second?

1. Energy

2. Torque

3. Acceleration

4. Momentum

Q. 113.When do we take reduced mass?

Q. A particle performs SHM of amplitude A along a straight line.When it is at a dis†an ce \sqrt3/2A from mean position , its kinetic energy gets incresed by an amount 1/2mω^2A^{2 }due to an impulsve force .Then its new amplitude becomes

Q. The door of an almirah is 6 ft high, 1⋅5 ft wide and weighs 8 kg. The door is supported by two hinges situated at a distance of 1 ft from the ends. If the magnitudes of the forces exerted by the hinges on the door are equal, find this magnitude.

Q. A current carrying square loop is placed near an infinitely long current carrying wire as shown in figure. The torque acting on the loop is

Q. An electric field of $1000\text{V/m}$, is applied to an electric dipole moment of ${10}^{-29}C\cdot m.$ What is the potential energy of the electric dipole?

1. $-10\times {10}^{-29}J$
2. $-9\times {10}^{-20}J$
3. $-20\times {10}^{-18}J$
4. $-7\times {10}^{-27}J$

Q. Calculate the total torque acting on the body shown in figure (10-E2) about the point O.

Figure

Q. A body staring from rest is accelerated by an applied force f aacting on it.If the mass of the object is m find the expression of displacement covered by the body in n seconds .Given the mass of body M

Q. At a point 'A' on the earth's surface, the angle of dip is $\delta =+25°$. At a point 'B' on the earth's surface, the angle of dip is$\delta =-25°$. We can interpret that

1. 'A' and 'B' are both located in the northern hemisphere.
2. 'A' is located in the southern hemisphere and 'B' is located in the northern hemisphere.
3. 'A' is located in the northern hemisphere and 'B' is located in the southern hemisphere.
4. 'A' and 'B' are both located in the southern hemisphere.

Q. When a force of 6⋅0 N is exerted at 30° to a wrench at a distance of 8 cm from the nut, it is just able to loosen the nut. What force F would be sufficient to loosen it if it acts perpendicularly to the wrench at 16 cm from the nut?

Figure

Q. Figure (8-E12) shows two blocks A and B, each of mass of 320 g connected by a light string passing over a smooth light pulley. The horizontal surface on which the block A can slide is smooth. Block A is attached to a spring of spring constant 40 N/m whose other end is fixed to a support 40 cm above the horizontal surface. Initially, the spring is vertical and unstretched when the system is released to move. Find the velocity of the block A at the instant it breaks off the surface below it. Take g = 10 m/s².

Q.

A constant torque acting on a uniform circular wheel changes its angular momentum from $A_0$ to 4 $A_0$ in 4 seconds, the magnitude of the torque is

1. 

2. 

3. 

4. 

Q. The torque of a force $\underset{F}{\to }$ about a point is defined as $\underset{\mathrm{\Gamma }}{\to }=\underset{r}{\to }\times \underset{F}{\to }$. Suppose $\underset{r}{\to },\underset{F}{\to }$ and $\underset{\mathrm{\Gamma }}{\to }$ are all nonzero. Is $r\times \underset{\mathrm{\Gamma }}{\to }\left|\right|\underset{F}{\to }$ always true? Is it ever true?

Q. A coil in the shape of an equilateral triangle of side $l$ is suspended between the pole pieces of a permanent magnet, such that magnetic field of intensity $B$ is along the plane of the coil. If due to a current $I$ in the triangle, a torque $\tau$ acts on it, then side $l$ of the triangle is :

1. $\frac{1}{\sqrt{3}}\left(\frac{\tau }{BI}\right)$
2. $2{\left(\frac{\tau }{\sqrt{3}BI}\right)}^{\frac{1}{2}}$
3. $\frac{2}{\sqrt{3}}{\left(\frac{\tau }{BI}\right)}^{\frac{1}{2}}$
4. $4{\left(\frac{\tau }{\sqrt{3}BI}\right)}^{\frac{1}{2}}$

Q. for a ring and a disc , if torque applied is different but they have the same kinetic energy , then the number of revolutions before coming to rest is same for both (or ) different for both?. kindly explain.

Q. A coil in the shape of an equilateral triangle of side $l$ is suspended between the pole pieces of a permanent magnet, such that magnetic field of intensity $B$ is along the plane of the coil. If due to a current $I$ in the triangle, a torque $\tau$ acts on it, then side $l$ of the triangle is :

1. $\frac{1}{\sqrt{3}}\left(\frac{\tau }{BI}\right)$
2. $2{\left(\frac{\tau }{\sqrt{3}BI}\right)}^{\frac{1}{2}}$
3. $\frac{2}{\sqrt{3}}{\left(\frac{\tau }{BI}\right)}^{\frac{1}{2}}$
4. $4{\left(\frac{\tau }{\sqrt{3}BI}\right)}^{\frac{1}{2}}$

Q. A wire of length L is bent in the form of a circular coil and current i is passed through it. If this coil is placed in a magnetic field then the torque acting on the coil will be maximum when the number of turns is

1. As large as possible
2. Any number
3. 2
4. 1

Q. The period of oscillation of a magnet of a vibration magnetometer is $2.45s$ at one place and $4.9s$ at the other. The ratio of the horizontal component of the earth’s magnetic field at the two places is

1. 1 : 4
2. 1 : 2
3. 2 : 1
4. 4 : 1