Physics

Rotational Mechanics and Machines

79 Questions

Rotational mechanics involves the study of angular motion, torque, gears, and rotational energy. These concepts are frequently tested in physics sections across various competitive assessments. Practicing these problems builds a strong foundation in machine kinematics and dynamics.

angular kinematicsgears and speedrotational energytorque calculationsmoment of inertia

Rotational Mechanics and Machines Questions

Multiple choice

In a wheel and axle arrangement, the diameter of wheel should be

  1. equal to the diameter of axle

  2. smaller than the diameter of axle

  3. more than the diameter of axle

  4. independent of axle

  5. dependent on the direction of movement
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In a wheel and axle arrangement, wheel is always bigger in diameter than axle.

Multiple choice

The standard rate of turn is

  1. 3 degrees per second

  2. 6 degrees per second

  3. 12 degrees per second

  4. 24 degrees per second
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Standard rate turn (also called Rate 1 turn) is 3 degrees per second, which completes a full 360-degree circle in exactly 2 minutes (3°/s × 120s = 360°). This is the reference turn rate used in instrument flying procedures. The other options are incorrect - 6°/s would be a Rate 2 turn (30 seconds per circle), while 12°/s and 24°/s are not standard aviation turn rates.

Multiple choice

Directions: In the following question, four statements are provided between an opening statement 1 and a closing statement 6. The statements are jumbled up and form a coherent paragraph when properly arranged. Select the alternative representing the proper and logical sequencing of these six taken together.

  1. Gears are toothed wheels that transmit force and motion of one rotating, geared shaft to another.

A. Depending on the relative sizes of the meshing gears, a variety of speed or force multiplications can be obtained.

B. For gearing, it is more common to speak of torque than force.

C. It is possible to simply change the direction of motion.

D. Teeth can be formed on the outside, as for external gears, or on the inside, as for internal gears.

  1. Torque is equal to force multiplied by distance from the point of force application to the centre of rotation.

  1. DCBA

  2. BCAD

  3. DACB

  4. ABCD
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Sentence B as well as 6 both describes the concept of Torque as implied in relation to gears, therefore, these two must come together. The order presenting such sequence is available in option (3), hence, it is the correct answer.

Multiple choice

An outward slope provided on the tread of the wheel is

  1. 1 in 5

  2. 1 in 10

  3. 1 in 20

  4. 1 in 25
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Railway wheels are coned at 1 in 20 to provide a slight outward slope on the tread. This coning helps keep the wheels centered on the track and prevents excessive rubbing against the rail face. The 1 in 20 slope is the standard used in railway engineering.

Multiple choice

The motion of the potters wheel is __________.

  1. periodic

  2. curvilinear motion

  3. rectilinear motion

  4. oscillatory motion

  5. circular motion
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

A motion in which a body moves along a fixed axis without changing its position is called a circular or rotatory motion. The potters wheel moves in this type of motion.

Multiple choice

Which of the following is a false statement in surface grinding?

  1. Axis of rotation of wheel is parallel to the surface being ground.

  2. The job is held on a table which can be moved.

  3. The speed of grinding wheel can be increased only upto a limit.

  4. Truing of wheel is done for proper balancing of the wheel.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Truing is the process of making the grinding wheel concentric with its axis of rotation, not for balancing. Balancing is a separate process to reduce vibration.

Multiple choice

A pinion with radius r1 and inertia l1 is driving a gear with radius r2 and inertia I2. Torque $\tau$1 is applied on pinion. The following are free body diagrams of pinion and gear showing important forces (F1 and F2) of interaction. Which of the following holds true?
  1. F1 $ \neq$F2; ![](https://i.imgur.com/01MDD9u.png); F2 = ![](http://i.imgur.com/4AcAOb7.png)

  2. F1 = F2; ; F2 =

  3. F1 = F2; ; F2 =

  4. F1 $ \neq$F2; ![](https://i.imgur.com/GD5j0Sd.png); F2 = ![](http://i.imgur.com/Tm4IKZx.png)
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation