“Rolling Motion” MHT-CET Class 12 Physics Crash Course| Chapter Rotational Dynamics
In this session G.S. Khairnar discussed the theory and MCQ’s of “Rolling Motion”. The session will be useful for all the aspirants of MHT-CET 2022. The session will be in Marathi and English.
Rolling Motion:-
Hello everyone, in previous articles we have learnt about the important parameters to discuss the rotational motion. In rotational motion moment of inertia and radius of gyration are two important factors which make large impact on explanation of rotational motion.
Kinetic energy of body of mass ‘M’ and velocity ‘v’ performing translational motion is given as,
Whereas the kinetic energy of body performing rotational motion is given as
Now consider an example of wheel moving on plane or inclined surface. Which type of motion is involved in it? Yes, it’s rolling motion.
Let’s discuss the rolling motion in details……!
Here we are going to discuss the rolling motion in two parts…!
1) Rolling motion of body on plane horizontal surface.
The rolling motion of a body is combination of translational motion and rotational motion. Thus the kinetic energy of rolling body is the sum of translational kinetic energy and rotational kinetic energy given as,
2) Rolling motion of body from plane inclined surface without slipping.
Consider a rigid body of mass ‘M’ and radius ‘R’ rolling down inclined plane of inclination ‘θ’ from height ‘h’ shown in a fig. below.
Body starts from rest and rolls down, it loses its gravitational potential energy. This potential energy is converted into kinetic energy.
If ‘V’ is the linear speed acquired by the body when it reaches the bottom of the inclined plane, then loss in potential energy = gain in kinetic energy.
Let ‘a’ be the linear acceleration of the body while rolling down the plane.
As the body starts forms rest, u = 0
∴ v2 = 0 + 2as where ‘S’ is the length of the plane.
This value changes with different geometrical shapes, just as given below…
Points to remember…..!
Rolling Motion:
Let’s solve the following MCQ’s…!
Q.1) Rolling motion is……….
a) rotational motion
b) translational motion
c) neither rotational nor translational
d) combination of both ‘a’ and ‘b’
Answer
d) combination of both ‘a’ and ‘b’
Q.2) Kinetic energy of rolling motion is ……….
a) translational kinetic energy
b) rotational kinetic energy
c) Sum of translational and rotational kinetic energy
d) Either rotational or translational
Answer
c) Sum of translational and rotational kinetic energy
Q.3) Kinetic energy of body rolling on plane, friction less and horizontal surface is……….
Q.4) Solid sphere of mass 200 g and radius 8 cm is rolling on plane horizontal surface at 12 m/s. Kinetic energy of sphere is ……….
a) 20 erg
b) 200 erg
c) 20 J
d) 200 J
Answer
c) 20 J
Q.5) Hollow cylinder of mass of radius 16 cm is rolling down from inclined and frictionless surface of height 2.5 m, speed of cylinder during motion is ( use g= 10 m/s2)……….
a) 5 cm/s
b) 5 m/s
c) 50 cm/s
d) 50 m/s
Answer
b) 5 m/s
Q.6) Ring and disc of equal radii and masses in ratio 2:3 are rolling on plane horizontal surface with velocities in ratio 3:2, then the ratio of kinetic energies of disc to ring is……
a) 4∶9
b) 2 :3
c) 9 :4
d) 3 :2
Answer
a) 4∶9
Q.7) Solid cylinder of radius 25 cm rolling from inclined surface of inclination 300 and height of 4 m, velocity and acceleration of cylinder before coming to rest is ( use g= 10 m/s2) ……
a) 5.30 m/s,3.30 m/s2
b) 3.30 m/s,7.30 m/s2
c) 7.30 m/s,3.30 m/s2
d) 3.30 m/s,5.30 m/s2
Answer
c) 7.30 m/s,3.30 m/s2
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