Bissoy.com
Doctors Medicines MCQs Q&A

A disc is undergoing pure rolling motion on a flat surface. The radius of the disc is 5cm & velocity of centre of mass is 10m/s. What is the ratio of kinetic energy as seen from the ground frame to a frame moving along the disc with a speed of 10m/s?

A disc is undergoing pure rolling motion on a flat surface. The radius of the disc is 5cm & velocity of centre of mass is 10m/s. What is the ratio of kinetic energy as seen from the ground frame to a frame moving along the disc with a speed of 10m/s? Correct Answer 3:1

The kinetic energy of a pure rolling disc as seen from the ground frame is given by: 1/2MV2 + 1/2Iw2. I = MR2/2 w = V/R ∴ 1/2MV2 + 1/2Iw2 = 1/2MV2 + 1/4MV2 = 3/4MV2. Kinetic energy as seen from the moving frame will only be the energy due to rotation about the disc’s axis. ∴ Kinetic energy from moving frame = 1/2Iw2 = 1/4MV2. ∴ Ratio = (3/4MV2) / (1/4MV2) = 3:1.

Related Questions

A disc is under pure rolling motion on a horizontal surface. The speed of the topmost point at an instant is 5m/s w.r.t the centre of the disc. What is the velocity of the centremost point? The radius of the disc is 10cm.
A solid sphere is given a horizontal velocity of 4m/s on a flat surface. What will be its velocity when it starts pure rolling? Mass = 2kg, Radius = 5cm. Coefficient of friction = 0.3.
A disc is standing on a flat rough surface. Its centre is suddenly given a velocity of 5m/s in the forward direction. In how much time will pure rolling start? Mass = 1kg, Radius = 10cm. Coefficient of friction = 0.4.
A semicircular disc rests on a horizontal surface with its top flat surface horizontal and circular portion touching down. The coefficient of friction between semi circular disc and horizontal surface is µ. This disc is to be pulled by a horizontal force applied at one edge and it always remains horizontal. When the disc is about to start moving, its top horizontal force will
A semi-circular disc rests on a horizontal surface with its top flat surface horizontal and circular portion touching down. The coefficient of friction between semi-cricular disc and horizontal surface is i. This disc is to be pulled by a horizontal force applied at one edge and it always remains horizontal. When the disc is about to start moving, its top horizontal force will
“What is the different between height and radius of solid cylinder?” Which of the following option is sufficient alone to find the answer? A) A solid cylinder is made by melting a solid sphere. The radius of cylinder is 3 times the radius of a circle whose area is 154 sq.m. Height of cylinder is equal to the height of cone whose volume is 2772 cubic meters. B) Area of a rectangle whose longer side is ¾ times the radius of a solid cylinder, is 168 sq.m and, Volume of solid cylinder is 2772 cubic meters and its height is 18 m. C) A metallic cone of radius 15m and height 35m is melted into the solid cylinder of radius equal to the radius of a circle whose area is equal to the area of rectangle whose sides are in the ratio 4 : 3 respectively. D) The curved surface area of the solid cylinder is 3 time the surface area of a sphere of radius 7m and height of cylinder is equal to the height of a metallic cone whose curved surface area is 308 sq.m. 
What is the distance covered by boat N upstream in 5 hours? Which of the following option is sufficient alone to find the answer? A) Boat M is travelling downstream with 20% more downstream speed of boat N. Speed of boat M in still water is 10% more than the speed of boat N in still water. B) Boat M and Boat N are travelling downstream with speed 33 km/hr and 40 km/hr respectively and speed of boat M is still water is 2 times the speed of stream. C) Speed of boat M in still water is 6 km/hr less then speed of boat N in still water and speed of stream is 10 km/hr. D) Speed of stream is ½ times the speed of boat N in still water and downstream speed of boat M is 44 km/hr. E) Speed of stream is 10 km/hr and ratio of upstream speed of boat M and boat N is 3 : 2 respectively.
A rider is riding his bike along the sides of a square ground. He drives the bike with the speed of 10 km/h along one side, 15 km/h along another side, 18 km/h along the third side, and 20 km/h along the last side and reaches the starting point. What is the average speed of the bike along the sides of the ground?
Consider the following statements: 1. The kinetic friction is always less than the rolling friction. 2. The kinetic friction is always equal to the rolling friction. 3. The kinetic friction is always greater than the rolling friction. Which of the following statement is correct?
A car is moving with constant linear acceleration a along horizontal X-axis. A solid sphere of mass M and radius R is found rolling without slipping on the horizontal floor of the car in the same direction as seen from an inertial frame outside the car. The acceleration of the sphere in the inertia frame is