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

An epicyclic gear train is shown schematically in the adjacent figure. The sun gear 2 on the input shaft is a 20 teeth external gear. The planet gear 3 is a 40 teeth external gear. The ring gear 5 is a 100 teeth internal gear. The ring gear 5 is fixed and the gear 2 is rotating at 50 rpm ccw (ccw = counter-clockwise and cw = clockwise) The arm 4 attached to the output shaft will rotate at

  1. 10 rpm ccw

  2. 10 rpm cw

  3. 12 rpm cw

  4. 12 rpm ccw
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Multiple choice

The number of inversions for a slider crank mechanism is

  1. 6

  2. 5

  3. 4

  4. 3
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

For a 4 bar slider crank mechanism, there are the number of links or inversions are 4. These different inversions are obtained by fixing different links once at a time for one inversion. Hence, the number of inversions for a slider crank mechanism is 4.

Multiple choice

A 1 kg mass of clay, moving with a velocity of 10 m/s, strikes a stationary wheel and sticks to it. The solid wheel has a mass of 20 kg and a radius of 1 m. Assuming that the wheel and the ground are both rigid and that the wheel is set into pure rolling motion, the angular velocity of the wheel immediately after the impact is approximately

  1. zero
  2. $\frac{1}{3}rad/s$
  3. $\sqrt{\frac{10}{3}}red/s$
  4. $\frac{10}{3}red/s$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Multiple choice

A band brake consists of a lever attached to one end of the band. The other end of the band is fixed to the ground. The wheel has a radius of 200 mm and the wrap angle of the band is 270°. The braking force applied to the lever is limited to 100N, and the coefficient of friction between the band and the wheel is 0.5. No other information is given.

The maximum tension that can be generated in the band during braking is

  1. 1200 N

  2. 2110 N

  3. 3224 N

  4. 4420 N
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Multiple choice

A band brake consists of a lever attached to one end of the band. The other end of the band is fixed to the ground. The wheel has a radius of 200 mm and the wrap angle of the band is 270°. The braking force applied to the lever is limited to 100 N, and the coefficient of friction between the band and the wheel is 0.5. No other information is given.

The maximum wheel torque that can be completely braked is

  1. 200 N.m

  2. 382 N.m

  3. 604 N.m

  4. 844 N.m
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Multiple choice gear torque

Two mating spur gears have 40 and 120 teeth respectively. The pinion rotates at 1200 rpm and transmits a torque of 20 Nm. The torque transmitted by gear is

  1. 7.0 Nm

  2. 20 Nm

  3. 35 Nm

  4. 60 Nm
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The gear ratio is the ratio of the number of teeth on the gear to the pinion (120/40 = 3). Since torque is proportional to the gear ratio, the torque on the gear is 3 times the torque on the pinion (20 Nm * 3 = 60 Nm).

Multiple choice mathematics and statistics angle and its measurement directed angles

If a bicycle wheel has 48 spokes the angle between the adjacent pair spokes is :

  1. $\left ( 6\frac{1}{2} \right )^0$
  2. $\left ( 7\frac{1}{2} \right )^0$
  3. $\left ( 7\frac{1}{3} \right )^0$
  4. $\left ( 6\frac{2}{3} \right )^0$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

required angle = $\frac{360}{48}$
$\frac{30}{4}$ = $\frac{15}{2}$= $\left ( 7\frac{1}{2} \right )^0$

Multiple choice motional emf physics

The axle of a circular wheel of radius R is held horizontally by two identical strings of equal lengths separated by a distance D. The tension in each string is $T _0$. The rim of the wheel carries a total charge $+$Q distributed uniformly on it. The wheel is vertical and is kept in a uniform vertical magnetic field $\vec{B}$. It is now rotated at an angular speed $\omega$. If the string break at a tension of $3T _0/2$, than the maximum possible value of $\omega$ at which the wheel can be rotated without breaking a string is $\dfrac{DT _0}{QBR^2}$.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer