Torque

Q.

State the different types of equilibrium.

Q.

Fig. 1.31 shows two forces each of magnitude 10 N acting at the points A and B at a separation of 50 cm, in opposite directions, Calculate the resultant moment of the two forces about the point (i) A, (ii) B and (iii) O situated exactly at the middle of the two forces.

Q.

Write the relation between angular momentum and torque.

Q.

A force $F=(i+2j+3k)N$ acts at a point $(4i+3j–k)m$. Then the magnitude of torque about the point $(i+2j+k)m$ will be$\sqrt{x}N–m$. The value of $x$ is

Q.

What is the SI unit of force?

Q.

A uniform metre scale can be balanced at the 70.0 cm mark when a mass of 0.05 kg is hung from the 94.0 cm mark. Find the mass of the metre scale.

1. 70 g

2. 80 g

3. 24 g

4. 60 g

Q.

The moment of a force of 10 N about a fixed point O is 5 Nm. Calculate the distance of the point O from the line of action of the force.

Q.

A nut is opened by a wrench of length 10 cm. If the least force required is 5.0 N, find the moment of force needed to turn the nut.

Q.

A charged particle moves through a region of magnetic field pointing in the direction perpendicular to its direction of velocity. Then during its subsequent motion,

(1)	Its momentum changes but the kinetic energy remains constant.
(2)	Its momentum and kinetic energy both changes.
(3)	Its momentum and kinetic energy both remains constant.
(4)	Its kinetic energy changes but the momentum remains constant.

Q.

A spanner (or wrench) has a long handle. Why?

Q.

A man can open a nut by applying a force of 150 N by using a lever handle of length 0. 4 m. What should be the length of the handle if he is able to open it by applying a force of 60 N?

1. 0.8 m

2. 1 m

3. 5 m

4. 2 m

Q.

The stone of a hand flour grinder is provided with a handle near its rim. Give reason.

Q.

Two forces each of magnitude 10 N act vertically upwards and downwards respectively at the two ends A and B of a uniform rod of length 4 m which is pivoted at its midpoint O as shown in the figure. Determine the magnitude of resultant moment of forces about the pivot O.

length 4 m which is pivoted at its mid point O as shown in Fig. 1.30. Determine the magnitude of resultant moment of forces about the pivot O.

Q.

A boy of mass 30 kg is sitting at a distance of 2 m from the middle of a seesaw. Where should a boy of mass 40 kg sit so as to balance the see-saw?

1. 2 m

2. 2.5 m

3. 1.5 m

4. 3 m

Q.

Two equal forces are acting at a point with an angle of $60°$ between them. If the resultant force is equal to $40\sqrt{3}N$, the magnitude of each force is

1. $40N$

2. $20N$

3. $80N$

4. $30N$

Q.

Is torque is a scalar or vector quantity?

Q.

A steering wheel of diameter $0.5m$ is rotated anticlockwise by applying two forces each of magnitude $5N$. Calculate the moment of couple applied.

1. $2.5Nm$

2. $4.5Nm$

3. $2.0Nm$

4. $4.0Nm$

Q.

State one way to obtain a greater moment of a force about a given axis of rotation.

Q.

State whether the moment of force is a scalar or vector quantity ?

Q.

A jack screw is provided with a long arm. Explain why ?

Q.

Three particles, each of mass m, are placed at the vertices of an equilateral triangle of side $a$. The net gravitational force on a body of mass $M$ at the centroid of the triangle is

1. $\frac{GmM}{a^2}$

2. $\frac{2GmM}{a^2}$

3. $\frac{3GmM}{a^2}$

4. zero

Q.

A uniform metre rule is pivoted at its mid - point. A weight of 50 gf is suspended at one end of it. Where should a weight of 100 gf be suspended to keep the rule horizontal ?

Q.

State one way to reduce the moment of a given force about a given axis of rotation.

Q.

A wheel of diameter 2 m is shown in the figure with an axle at O. A force F = 2 N is applied at B in the direction shown in figure. Calculate the moment of force about (i) the centre O, and (ii) the point A.

Q. A bird weighs 2kg and is inside a closed case of 1 Kg. If it starts flying then what is the weight of the bird and cage assmbly
(A) 1.5 kg (B) 2.5kg (C) 3 kg (D) 4kg

Q.

A ring with radius $4m$ is hinged at point P. Two forces $F_1$ and $F_2$, each of magnitude $10N$ acts on the Ring. Find the ratio of the torques produced by two forces $F_1$ to $F_2$ is

1. $3:1$

2. $1:3$

3. $2:1$

4. $1:2$

Q.

A couple produces

1. Linear and rotational motion

2. No motion

3. Purely linear motion

4. Purely rotational motion

Q.

Write the expression for the moment of force about a given axis.

Q.

Calculate the resultant moment of forces about the point B.

1. 10 Nm

2. 8 Nm

3. 20 Nm

4. 5 Nm

Q.

Three particles, each of mass m, are placed at the vertices of an equilateral triangle of side a. The gravitational field intensity at the centroid of the triangle is

1. zero

2. $\frac{G{m}^2}{a^2}$

3. $\frac{2G{m}^2}{a^2}$

4. $\frac{3G{m}^2}{a^2}$