Q: What is time?

D = R \times T In this equation Distance, and Time both are variable that can change. Time changes with the velocity. The faster something travels the slower time changes. At the speed of light time stops and no longer exists. For light or anything without mass that achieves the speed of light time does not exist.Without space it is difficult to imagine how time could exist. The fourth dimension is part of the the other three dimensions. Before the beginning of the present universe ( The Big Bang?) neither time nor space existed.Time is a variable it can change with both mass and velocity. Time is a part of space and is considered to be the fourth dimension of the universe.

Question 1

The dimensions of Planck's constant is

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Question 2

What is time?

Accepted Answer

D =  R 	imes T  In this equation Distance, and Time both are variable that can change. Time changes with the velocity. The faster something travels the slower time changes. At the speed of light time stops and no longer exists. For light or anything without mass that achieves the speed of light time does not exist.Without space it is difficult to imagine how time could exist. The fourth dimension is part of the the other three dimensions. Before the beginning of the present universe ( The Big Bang?) neither time nor space existed.Time is a variable it can change with both mass and velocity. Time is a part of space and is considered to be the fourth dimension of the universe.

Question 3

All the surfaces shown in figure (12-E15) are frictionless. The mass of the car is M, that of the block is m and the spring has spring constant k. Initially, the car and the block are at rest and the spring is stretched through a length $x_{0}$ when the system is released.
Find the time period(s) of the two simple harmonic motions.

Accepted Answer

At any position, let the velocities be  v_{1}  and  v_{2}  respectively.Here,  v_{1}=  velocity of  m  with respect to  M .By energy methodTotal Energy = Constant (1/2)Mv^{2}+(1/2)m(v_{1}-v_{2})^{2}+(1/2)k(x_{1}+x_{2})^{2}=  Constant ..(i)[ v_{1}-v_{2}=  Absolute velocity of mass  m  as seen from the road.]Again, from law of conservation of momentum mx_{2}=mx_{1}\Rightarrow x_{1}=\dfrac{M}{m}x_{2}        ....(1) mv_{2}=m(v_{1}-v_{2})\Rightarrow (v_{1}-v_{2})=\dfrac{M}{m}v_{2}       .....(2) Putting the above values in equation  (1) , we get \dfrac{1}{2}Mv_{2}^{2}+\dfrac{1}{2}m\dfrac{M^{2}}{m^{2}}v_{2}^{2}+\dfrac{1}{2}kx_{2}^{2}\left(1+\dfrac{M}{m}ight)^{2}=  constant 	herefore M\left(1+\dfrac{M}{m}ight)v_{2}+k\left(1+\dfrac{M}{m}ight)^{2}x_{2}^{2}=  Constant. mv_{2}^{2}+l\left(1+\dfrac{M}{m}ight)x_{2}^{2}=  constantTaking derivative of both sides, M	imes 2v_{2}\dfrac{dv_{2}}{dt}+k\dfrac{(M+m)}{m}--ex_{2}^{2}\dfrac{dx_{2}}{dt}=0 \Rightarrow ma_{2}+k\left(\dfrac{M+m}{m}ight)x_{2}=0  [because,  c_{2}=\dfrac{dx_{2}}{dt} ]Taking derivative of both sides, M	imes 2v_{2}\dfrac{dv_{2}}{}+k\dfrac{(M+m)}{m}-ex_{2}^{2}\dfrac{dx_{2}}{dt}=0 \Rightarrow ma_{2}+k\left(\dfrac{M+m}{m}ight)x_{2}=0   [because,  v_{2}=\dfrac{dx_{2}}{dt} ] \Rightarrow \dfrac{a_{2}}{x_{2}}=-\dfrac{k(M+m)}{Mm}=\omega^{2} 	herefore \omega=\sqrt{\dfrac{k(M+m)}{Mm}} So, Time period,  T=2\pi \sqrt{\dfrac{Mm}{k(M+m)}}

Question 4

Choose the correct answer from the alternatives given.Time period is the time taken to complete one oscillation. This definition of time period is true for

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Question 5

An object is placed at a distance of 10 cm from a concave mirror of focal length 20 cm.
a) Draw ray diagram for the formation of image
b) Calculate the image distance
c) state 2 characteristics of the image formed.

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Given: Focal length of concave mirror, f = -20 cmDistance of object from the mirror, u = -10 cmuse formula, 1/v + 1/u = 1/f or, 1/v = 1/f - 1/u or, 1/v = 1/-20 - 1/-10 or, 1/v = -1/20 + 1/10 = 1/20 or, v = +20cm hence, image position is the 20cm right side from the pole of the concave mirror as shown in the diagram. The image is straight and bigger than the object.

Question 6

Why is acceleration measured in meters / seconds squared?

Accepted Answer

AnswerBecause acceleration is velocity in m/s divided by time in s, the SI units for acceleration are m/s2, meters per second squared or meters per second per second, which literally means by how many meters per second the velocity changes every second.

Question 7

What is the unit of viscosity? Please explain.

Accepted Answer

The viscosity of a fluid is a measure of its resistance to flow.We usually think of the viscosity of a liquid as its "thickness".For example, we say that honey is "thicker" (has a higher viscosity) than water.One way to measure viscosity is to place the fluid between two flat parallel plates and slide one plate past the other.In terms of the above diagram, the formula for viscosity η is   \eta = \frac { F \delta }{Av }  Thus the units of visocity are   \frac { N 	imes m}{ m^2 	imes  m . s^{-1} }= N.sm.m^{-2} = P a.s  If a fluid is placed between two    1m^2   plates that are 1 m apart and one plate is pushed sideways with a force of 1 N and it moves at a velocity of   1 m/s^{-1}   then the fluid has a viscosity   \eta  = 1 Pa.s  Many chemists still use an old unit of viscosity, the poise (P), named after the French physician Jean Poiseuille.It is convenient unit because   1m Pa.s = 1cP  For example , the viscosity of water at   20^0 C   is    1.002 mPa.s   or   1.002 cP  Honey has a viscosity of about   10 Pa.s   or   10000cP

Question 8

Which is warmer -30C or -30 F?

Accepted Answer

Answer :  30^{\circ}C Explanation: Because if we convert  -30^{\circ}F  to celusis by ,  \dfrac{C}{100} = \dfrac{F - 32}{180}   we get -  30^{\circ}F   equal to  -30^{\circ}C -30^{\circ}C = - 22^{\circ} F   So  	herefore   we can say  -30^{\circ}C  is warmer

Question 9

All the surfaces shown in figure (12-E15) are frictionless. The mass of the car is M, that of the block is m and the spring has spring constant k. Initially, the car and the block are at rest and the spring is stretched through a length $x_{0}$ when the system is released.
Find the amplitudes of the simple harmonic motion of the block and of the car as seen from the road.

Accepted Answer

Let the amplitude of oscillation of  m  and  M  be  x_{1}  and  x_{2}  respectively.a) From law of conservation of momentum, mx_{1}=Mx_{2}   ...(1)   [because only internal forces are present]Again  (1/2)kx_{0}^{2}=(1/2)k(x_{1}+x_{2})^{2} [Block and mass oscillates in opposite direction, But  xightarrow  stretched part]From equation  (1)  and  (2) 	herefore x_{0}=x_{1}+\dfrac{m}{M}x_{1}=\left(\dfrac{M+m}{M}ight)x_{1} 	herefore x_{1}\dfrac{Mx_{0}}{M+m} So,  x_{2}=x_{0}=x_{0}\left[1-\dfrac{M}{M+m}ight]=\dfrac{mx_{0}}{M+m}  respectively.

Question 10

What does the chemical symbol Fe stand for?

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Basic Science

General Knowledge
1667 Views

The dimensions of Planck's constant is

What is time?

Choose the correct answer from the alternatives given.
Time period is the time taken to complete one oscillation. This definition of time period is true for

An object is placed at a distance of 10 cm from a concave mirror of focal length 20 cm.
a) Draw ray diagram for the formation of image
b) Calculate the image distance
c) state 2 characteristics of the image formed.

Why is acceleration measured in meters / seconds squared?

What is the unit of viscosity? Please explain.

Which is warmer -30C or -30 F?

What does the chemical symbol Fe stand for?

Basic Science

General Knowledge 1667 Views

The dimensions of Planck's constant is

What is time?

Choose the correct answer from the alternatives given. Time period is the time taken to complete one oscillation. This definition of time period is true for

An object is placed at a distance of 10 cm from a concave mirror of focal length 20 cm. a) Draw ray diagram for the formation of image b) Calculate the image distance c) state 2 characteristics of the image formed.

Why is acceleration measured in meters / seconds squared?

What is the unit of viscosity? Please explain.

Which is warmer -30C or -30 F?

What does the chemical symbol Fe stand for?

General Knowledge
1667 Views

Choose the correct answer from the alternatives given.
Time period is the time taken to complete one oscillation. This definition of time period is true for

An object is placed at a distance of 10 cm from a concave mirror of focal length 20 cm.
a) Draw ray diagram for the formation of image
b) Calculate the image distance
c) state 2 characteristics of the image formed.