Intro to Torque

Q.

Four forces P, 2P, 3P and 4P act along sides of a square taken in order. Find their resultant.

1. 

2. 

3. 

4. 

Q.

The mass of the moon is 1/81 of earth's mass and its radius 1/4 that of earth. If the escape velocity from the earth's surface is 11.2 km/s , its value for the moon...

1. 0.5 km/s

2. 5.0 km/s

3. 0.14 km/s

4. 2.5 km/s

Q. If spinning speed of the earth is decreased, then weight of the body at the poles does not change .Why?

Q. the magnitude of torque on a particle of mass 1 kg is 2.5 N-m about tho origin. If the force acting on it is 1N and the distance of the particle from the origin is 5m, then find the angle between the force and position vector .

Q. A body of mass m crosses the topmost point of a vertical circle with critical speed. What is the torque about the centre at this instant?

Q. arter28 A body of mass 5 kg hangs from a spring andoscillates with a time period of 2Tt second. If thebody is removed, the length of the spring willdecrease by40(1) glk metre(2) klg metre

Q. a yo yo has aspool of mass m and radius R. a massless string is wound around an axle of radius b and of negligible mass.if the yo yo released from rest has a downward acceleration of g/9 what is the ratio of R/b?

Q. A thin uniform rod of length 1m and mass 500 g is attached to a uniform disc of diameter 20 cm and mass 100 g at one end as shown in the figure. The dis†an ce of center of mass from the free end of the rod is

Q. A sImple pedulum consists of a 2.0 ka mass attached to a string. it is released from rest at X as shown.ts speed at the lowest point Y is1.85 my(2) 3.6 m/s(1) 0.90 m/s(4) 6.0 m/s(3) 3.6 m/s(5) 36 m/s

Q. Moment of force $\left(\overrightarrow{F}\right)$ about an axis $\left(\overrightarrow{AB}\right)$ is zero when

1. $\overrightarrow{F}||\overrightarrow{AB}$
2. $\overrightarrow{F}$ intersects $\overrightarrow{AB}$
3. $\overrightarrow{F}\perp \overrightarrow{AB}$
4. Both (a) and (b)

Q. A door $1.6\text{m}$ wide requires a minimum force of $1\text{N}$ to be applied at the free end to open or close it. The minimum force that is required at a point $0.4\text{m}$ away from the hinges for opening or closing the door is

1. $1.2\text{N}$
2. $2.4\text{N}$
3. $3.6\text{N}$
4. $4\text{N}$

Q. Find the total torque acting on the body shown in the figure about the point $O$

1. $2Fr\text{N-m}$
2. $Fr\text{N-m}$
3. $0\text{N-m}$
4. $\frac{Fr}{2}\text{N-m}$

Q. A father racing with his son, has 1/3 of KE of his son, who has 1/3 the mass of the father.The father speeds up by 2 m/s and then has the same KE as that of the son.The initial speeds of the father and the son are

Q. are trolley of mass 1 kg is connected to Spring identical spring of spring constant hundred Newton per metre is true if the role is displaced by its mean position by 1 centimetre then maximum values to the trolley will be

Q. A block of mass m kg is kept on a weighing machine in an elevator. If the elevator is retarding upward by a ms2, the reading of weighing machine is (in kgf)(1) mg(2) m(g - a)am 1(4) m(g+ a)3)

Q. For a force $F$ acting on rigid body,
Statement $1:$ Component of torque about any point lying on the axis, along the axis is defined as torque about that axis.
Statement $2:$ Torque about an axis is same as torque about any point lying on that axis.

1. Statement $1$ is correct and statement $2$ is incorrect
2. Statement $1$ is incorrect and statement $2$ is correct
3. Both statements are correct.
4. Both statements are incorrect.

Q. a solid cylinder of mass 2kg and radius 50cm rolls up an inclined plane of angle of inclination 30 degree the centre of mass of cylinder has speed of 4m\s the distance travelled by the cylinder surface will be

Q.

A 2 m rod of mass 1 kg rotates at an angular speed of 15 rad/s about its ends. Then K.E. is

1. 150 J

2. 100 J

3. 1500 J

4. 1.5 J

Q. A block of mass m kg is kept on a weighing machine in an elevator. If the elevator is retarding upward by a ms^{-2}the reading of weighing machine is (in kgf)(1) mg(2)m(g - a) (3) m(1-a/g)(4) m(g+ a)

Q. A bullet of mass 0.02 kg is moving with a speed of 10 m/s. It can penetrate 10 cm of a wooden block and come to rest. If the thickness the target would be 6 cm only find the KE of the bullet when it comes out.

Q. 24) b. Determine the escape speed of moon. Give the radius of moon is $1.74\times {10}^{6}m$ and its mass is $7.36\times {10}^{22}kg.$

Q. 14.A light string passing over a smooth light pulley connects two blocks of masses M1 and M2. If the acceleration of the system is g/8, then the ratio of masses is ? Consider M1> M2

Q. A body of moment of inertia of $3k\times m^2$ rotating with an angular speed of $2rad/sec$ has the same KE as a mass of $12kg$ moving with a speed of :

Q. What is the torque produced by a force about the origin when it is directed towards the origin?

1. Positive
2. Negative
3. Zero
4. Depends, cannot say

Q. Twa blocks of massos 10 ka and 9 ka arewith ligtit string which is passing over sn ideal putleyas shown in figure. If system is released from restthen the acceleration of o kg block at the ginstant is about (Assume all the surfaces aresmooth and g-10 m/s2)AL10 kg(2) 42 m/(4) 3 misł35 m/s

Q.

A particle of mass M is released in vertical plane from a point P at $x$ = $x_0$ on the axis it falls vertically

along the y-axis. Find the torque $\tau$ acting on the particle at a time t about origin?

1. $mg{x}_0\hat{k}$

2. $-mg{x}_0\hat{k}$

3. $2mg{x}_0\hat{k}$

4. $3mg{x}_0\hat{k}$

Q. The analogous to Force in rotation is

1. Angular momentum
2. Torque
3. Angular acceleration
4. Moment of inertia

Q. Find the torque by the force, $\overrightarrow{F}=2\hat{i}+3\hat{j}+5\hat{k}$ acting at the point $\overrightarrow{r_1}=5\hat{i}+2\hat{j}-\hat{k}$ about the point $\overrightarrow{r_2}=6\hat{i}-4\hat{j}+\hat{k}$.

1. $15\hat{i}+\hat{j}+36\hat{k}$
2. $36\hat{i}+\hat{j}-15\hat{k}$
3. $36\hat{i}-15\hat{j}+\hat{k}$
4. $\hat{i}+36\hat{j}-15\hat{k}$

Q. there are two object of mass 20kg and 300kg. let m_1=20kg and m_2=300kg. what is the acceleration by which object of mass 20kg will be attracted to the mass of 300kg. also find the acceleration by which 300kg mass will be attracted towqrds 20kg

Q. A pulley of radius $2\text{m}$ is rotated about its axis by a force $F=(20t-5t^2)\text{N}$ (where $t$ is measured in seconds) applied tangentially. If the moment of inertia of the pulley about its axis of rotation is $10{\text{kgm}}^2$, the number of rotations made by the pulley before its direction of motion is reversed, is

1. Less than 3
2. More than 3 but less than 6
3. More than 6 but less than 9
4. More than 9