Mechanics | Relativity Answers

What is the main difference between gravitation and gravity, weight

As shown in figure, there is a flat plank at rest on a very slippery surface. You have disc of radius a and mass equal to the mass of the disc (say M). You rotated the disc with an initial angular speed

and carefully placed it on the plank. The coefficient of friction between the disc and plank is #. You noticed that, finally when the slipping stops, the 50% of the total kinetic energy of the system is lost. If the plank is long enough, determine the time when slipping stops after placing the disc:

A wire M of diameter d is joint to another wire N of the same material. The diameter of N is half that of M but the two wires have the same length, If a steady potential difference is applied across the ends of the composite wire, which of the following statements is correct?

A. The current in N is half of the current in M

B. The drift velocity of the electrons in N is four times that of the electrons in M.

C. The number of charge carriers per unit length in M is twice that in N

D. The drift velocity of the electrons in M is twice that of the electrons in N

Which of the following statements is correct? During a change of state:

A.The internal energy of a system increases

B. Latent heat is absorbed

C. Work is done and bonds are broken

D. Work is done and /or bonds are being broken or constructed

Intensity is defined as power per unit area, What is the units of intensity?

A piece of Copper of mass 100g is heated to 100⁰C and transferred to a well lagged Copper can of 50g containing 200g of water at 10⁰C. The final temperature of the water is 14⁰C after stirring neglecting heat losses, calculate the specific heat capacity of copper using either mixing method or electrical method. State clearly the precautions you will take. The specific heat capacity of water = 4.2 x 10²Jkg^-1K^-1

2.5kg of water is heated in an open container for 5 minutes using a heater of power 2KW. Which of the following statements about the temperature of the water is true?(the SHC of water= 4200Jkg-1k-1)

A. The change in temperature of the water is 58.30C

B. The change in temperature of the water is 57.30C

C. The change in temperature of the water is greater 57.30C

D.If the initial temperature of the water was 23.70C then its final temperature would be 8100C

Which of the following statements about heat transfer is NOT true?

A. Radiation transmits heat through air with the speed of light in air

B. In a fluid, heat is transmitted upwards mainly by mass movement of fluid molecules

C. A poor conductor has a low value of thermal conductivity

D. All good thermal conductors are not necessarily good electrical conductors

A wire M of diameter d is joint to another wire N of the same material. The diameter of N is half that of M but the two wires have the same length, If a steady potential difference is applied across the ends of the composite wire, which of the following statements is correct?

A. The current in N is half of the current in M

B. The drift velocity of the electrons in N is four times that of the electrons in M.

C. The number of charge carriers per unit length in M is twice that in N

D. The drift velocity of the electrons in M is twice that of the electrons in N