Moment of a force, torque and angular momentum - One Line Questions
1.
A force F = (2i + 3j) N acts at a point r = (4i + 2j) m. The torque about the origin is: —
-8k N m
2.
If a body is rotating with angular velocity ω and has moment of inertia I, its rotational kinetic energy is given by: —
1/2 I ω^2
3.
A force of 10 N acts at a point P which is 2 m away from a pivot O. If the angle between the force vector and the position vector OP is 30 degrees, what is the magnitude of the torque? —
10 N m
4.
A force of 5 N acts on a position vector of (3i + 4j) m. The torque produced about the origin is: —
-15 k N m
5.
The angular momentum of a particle about the origin is L. If the particle moves to a new position such that its position vector is doubled, while its momentum remains the same, the new angular momentum will be: —
2L
6.
A force of 10 N is applied tangentially to a wheel of radius 0.5 m. The torque produced is: —
5 N m
7.
A force of 10 N is applied at a distance of 5 m from the pivot. What is the magnitude of the torque if the force is perpendicular to the lever arm? —
50 N m
8.
A force F acts at a distance r from a pivot. The torque is maximum when the angle between F and r is: —
90 degrees
9.
If the angular momentum of a system changes, it means that: —
A net external torque is acting on the system
10.
If no external torque acts on a system of particles, which quantity is conserved? —
Angular momentum
11.
Which quantity is conserved in a system upon which no external torque acts? —
Angular momentum
12.
When the net torque on a system is zero, the quantity that remains constant is: —
Angular momentum
13.
Angular momentum is related to the rotational inertia and: —
Angular velocity
14.
The direction of angular momentum vector is typically taken along the: —
Axis of rotation
15.
If the moment of inertia of a rotating body is halved, and its angular momentum remains constant, its angular velocity will: —
Double
16.
A couple consists of two forces which are: —
Equal in magnitude, opposite in direction, and acting along different lines
17.
Torque is the rotational analogue of which linear quantity? —
Force
18.
The moment of a force is defined as the product of: —
Force and perpendicular distance from the pivot to the line of action of the force
19.
If a force F is applied at a distance r, and F is perpendicular to r, the magnitude of torque is: —
Fr
20.
A spinning ice skater pulls her arms in to decrease her moment of inertia. According to the conservation of angular momentum, her angular velocity will: —
Increase
21.
If the net torque on a system is zero, then the angular momentum of the system: —
Is conserved
22.
What happens to the torque if the perpendicular distance from the pivot to the line of action of the force is doubled? —
It doubles
23.
Which of the following statements about angular momentum is correct? —
It is the product of moment of inertia and angular velocity.
24.
The SI unit of angular momentum is: —
Joule-second (J s)
25.
A particle of mass 2 kg is moving with a velocity of (3i + 4j) m/s. Its angular momentum about the origin is: —
k (24i - 18j) kg m^2/s
26.
Which of the following quantities is a vector quantity? —
Moment of a force
27.
A particle is rotating in a circle of radius r with constant speed v. Its angular momentum about the center of the circle is: —
mvr
28.
What is the condition for a rigid body to be in rotational equilibrium? —
Net torque acting on the body is zero
29.
Which of the following is a unit of torque? —
Newton-meter
30.
Which of the following is NOT a unit of torque? —
Joule
31.
What is the SI unit of the moment of a force (torque)? —
Newton-meter (N m)
32.
The conservation of angular momentum is a consequence of which law of physics? —
Newton's third law
33.
The moment of a couple is equal to the product of the magnitude of one force and the: —
Perpendicular distance between the lines of action of the two forces
34.
What is the direction of torque when a force is applied to rotate an object counter-clockwise? —
Perpendicular to the plane of rotation, out of the plane
35.
Angular momentum of a particle is defined as the product of: —
Position vector and linear momentum
36.
For a particle of mass m moving with velocity v at a position vector r from the origin, the angular momentum L is given by: —
r × (mv)
37.
If a force F acts at a position vector r from the pivot, the torque is given by: —
r × F
38.
If the position vector of a particle is r and its linear momentum is p, its angular momentum L is given by: —
r × p
39.
If a force F acts at a distance r, and the angle between r and F is θ, the magnitude of torque is given by: —
rF sin(θ)
40.
When a body is subjected to a torque, its angular momentum changes at a rate equal to: —
The applied torque
41.
The angular momentum of a particle is conserved if: —
The net external torque acting on it is zero
42.
A rigid body is rotating with constant angular velocity. This implies that: —
The net torque acting on it is zero
43.
The rate of change of angular momentum of a particle is equal to: —
The net torque acting on the particle
44.
The angular momentum of a particle about a point O is zero if: —
All of the above
45.
The angular momentum of a particle is zero if: —
All of the above
46.
For a particle moving in a circle of radius R with speed v, its angular momentum about the center of the circle is proportional to: —
v
47.
If a force is applied along the line passing through the pivot, the torque produced is: —
Zero
48.
A particle of mass m is projected with velocity v at an angle θ with the horizontal. What is its angular momentum about the point of projection when it reaches the highest point of its trajectory? —
Zero
49.
What is the angular momentum of a particle of mass m moving with velocity v in a straight line, about a point P on the line of motion? —
Zero
50.
The angular momentum of a particle about a point O is given by L = r × p. If the particle moves such that its velocity vector is always parallel to the position vector, its angular momentum about O will be: —
Zero