Home
Class 11
PHYSICS
As mosquito is sitting on an L.P. record...

As mosquito is sitting on an L.P. record disc rotating on a turn table at `33 1/3` revolutions per minute. The distance of the mosquito from the center of the turn table is 10 cm. Show that the friction coefficient between the record and the mosquito is greater than `pi^2/81`. Take `g=10m/s^2`

Text Solution

Verified by Experts

The correct Answer is:
A
A mosquito is sitting on an L.P record disc and rotating on a turn table at `33 1/2` rpm.
`n=33/1/3 rpm`
`100(3xx60)rps`
`:. omega==2pixx100/180`
`=(10pi)/9 rad/sec`
`r=10cm=0.4m`
`g=10 m/sec^2`
`mumg?=mromega^2`
`:. mugt(romega^2)/g.=(0.1xx(10pi/9)^2)/10`
`rarr mugt(pi^2/81)`
Promotional Banner

Similar Questions

Explore conceptually related problems

The fricition coefficient between the table and block shown in fig. is 0.2 find the acceleration of the system (Take g=10 m//s^(2) )

Find the maximum speed at which a car can take turn round a curve of 30 cm radius on a level road if the coefficient of friction between the tyres and the road is 0.4. Take g = 10 ms^(-2) .

A block of mass m = 20 kg is kept is a distance R = 1m from central axis of rotation of a round turn table (A table whose surface can rotate about central axis). Table starts from rest and rotates with constant angular acceleration, alpha = 3 rad//sec^(2) . The friction coefficient between block and table is mu = 0.5 . At time t = (x)/(30) from starting of motion (i.e. t =0) the block is just about to slip. Find the value of x (g = 10 m//s^(2))

A disc is rotatin g aro u n d its cen tre in a horizontal plane at the rate of 60 rotation/ minute. A coin (1A^(st)) is placed at a distance of 18 cm and 2^(nd) similar coin 20 cm from its centre. The co-efficient of static friction between the disc and the coins is 0.2. Which coin will be thrown away from the disc ? Which coin will keep rotating with the disc ?

Two blocks of masses 2kg and M are at rest on an inclined plane and are separated by a distance of 6.0m as shown. The coefficient of friction between each block and the inclined plane is 0.25 . The 2kg block is given a velocity of 10.0m//s up the inclined plane. It collides with M, comes back and has a velocity of 1.0m//s when it reaches its initial position. The other block M after the collision moves 0.5m up and comes to rest. Calculate the coefficient of restitution between the blocks and the mass of the block M. [Take sintheta=tantheta=0.05 and g=10m//s^2 ]

Two blocks of mass m_(1)=10kg and m_(2)=5kg connected to each other by a massless inextensible string of length 0.3m are placed along a diameter of the turntable. The coefficient of friction between the table and m_(1) is 0.5 while there is no friction between m_(2) and the table. the table is rotating with an angular velocity of 10rad//s . about a vertical axis passing through its center O . the masses are placed along the diameter of the table on either side of the center O such that the mass m_(1) is at a distance of 0.124m from O . the masses are observed to be at a rest with respect to an observed on the tuntable (g=9.8m//s^(2)) . (a) Calculate the friction on m_(1) (b) What should be the minimum angular speed of the turntable so that the masses will slip from this position? (c ) How should the masses be placed with the string remaining taut so that there is no friction on m_(1) .

Two metallic plate A and B , each of area 5 xx 10^(-4)m^(2) , are placed parallel to each at a separation of 1 cm plate B carries a positive charge of 33.7 xx 10^(-12) C A monocharonatic beam of light , with photoes of energy 5 eV each , starts falling on plate A at t = 0 so that 10^(16) photons fall on it per square meter per second. Assume that one photoelectron is emitted for every 10^(6) incident photons fall on it per square meter per second. Also assume that all the emitted photoelectrons are collected by plate B and the work function of plate A remain constant at the value 2 eV Determine (a) the number of photoelectrons emitted up to i = 10s, (b) the magnitude of the electron field between the plate A and B at i = 10 s, and (c ) the kinetic energy of the most energotic photoelectrons emitted at i = 10 s whenit reaches plate B Negilect the time taken by the photoelectrons to reach plate B Take epsilon_(0) = 8.85 xx 10^(-12)C^(2)N- m^(2)

An object A is kept fixed at the point x= 3 m and y = 1.25 m on a plank p raised above the ground . At time t = 0 the plank starts moving along the +x direction with an acceleration 1.5 m//s^(2) . At the same instant a stone is projected from the origin with a velocity vec(u) as shown . A stationary person on the ground observes the stone hitting the object during its downward motion at an angle 45(@) to the horizontal . All the motions are in the X -Y plane . Find vec(u) and the time after which the stone hits the object . Take g = 10 m//s

A circus wishes to develop a new clown act. Fig. (1) shows a diagram of the proposed setup. A clown will be shot out of a cannot with velocity v_(0) at a trajectory that makes an angle theta=45^(@) with the ground. At this angile, the clown will travell a maximum horizontal distance. The cannot will accelerate the clown by applying a constant force of 10, 000N over a very short time of 0.24s . The height above the ground at which the clown begins his trajectory is 10m . A large hoop is to be suspended from the celling by a massless cable at just the right place so that the clown will be able to dive through it when he reaches a maximum height above the ground. After passing through the hoop he will then continue on his trajectory until arriving at the safety net. Fig (2) shows a graph of the vertical component of the clown's velocity as a function of time between the cannon and the hoop. Since the velocity depends on the mass of the particular clown performing the act, the graph shows data for serveral different masses. From figure 2, approximately how much time will it take for clown with a mass of 60 kg to reach the safety net located 10 m below the height of the cannot?

Thin films, including soap bubbles and oil slicks, show patterns of alternating dark and bright regions resulting from interference among the reflected light waves. If two waves are in phase their crest and troughs will coincide. The interference will be constructive and the aplitude of the resultant wave will be greater than the amplitude of either constituent wave. if the two waves are out of phase, the crests of one wave will coincide with the troughs of the other wave. The interference will be destructive and the amplitude of the resultant wave will be less than that of either constituent wave. at the interface between two transparent media some light is reflected and some light is refracted. * When incident light, reaches the surface at point a, some of the light is reflected as ray R_(a) and and some is refracted following the path ab to the back of the film. *At point b some of the light is refracted out of the film and part is reflected back refracted out of the fiml as ray R_(c) . R_(a) and R_(c) are parallel. However, R_(c) has travelled the extra distance within the film of abc. if the angle of incidence is small then abc is approximately twice the film's thickness. if R_(a) and R_(c) are in phase they will undergo constructive interference and the region ac will be bright if R_(a) and R_(c) are out of phase, they will undergo destructive interference. * Refraction at an interface never changes the phase of the wave. * For reflection at the interface between two media 1 and 2, if n_(1)ltn_(2) the reflected wave will change phase by pi . if n_(1)gtn_(2) the reflected wave will not undergo a phase change. for reference n_(air)=1.00 * if the waves are in phase after refection at all interfaces, then the effects of path length in the film are Constructive interference occur when (n= refractive index) 2t=mlamda//n" "m=0,1,2,3... .. Destructive interference occurs when 2t=(m+1//2)lamda//n" "m=0,1,2,3... Q. The average human eye sees colors with wavelengths between 430 nm to 680 nm. For what visible wavelength will a 350 nm thick n=1.35 soap film produce maximum destructive interference?