Mechanics | Relativity Answers

An automobile of mass 10³kg moves with a velocity of 60m/s. The driver applies the brakes to reduce the velocity to 20m/s. What is the energy dissipated during the application of the brakes?

In which cases is there an attractive force?

A.   Two parallel beam of electrons with the same velocity

B.    Two parallel beam wires carrying current in opposite directions

C.    Two parallel beam of electrons in opposite directions

D.   A wire carrying current and a beam of parallel electrons in the same direction as the current.

E.    Wire carrying current and a beam of parallel electrons in opposite direction to the current.

Given a copper-nickel wire (of resistivity=0.4Ωmm²m^-1), cross-sectional area 0.1mm² and length 3.5m. It's resistance is ?

What is the instantaneous velocity (in m/s) of a coconut falling vertically from a coconut tree after 2 2,0s?

A current, I=200A is passed through a copper conductor of cross section: S=1cm². We suppose that all the atoms are transformed into Cu²⁺ ions. The density of copper is given by 8.9x10³kg/m³ ; ( atomic mass is M=0.0635kg/mol and the Avogadro number is N=6.22x10³ mol^-1. Calculate the number of electrons per m³:

On a plane inclined at an angle α=30⁰ to the horizontal, a small object of mass m=100mg is released and it slides without friction (given that g=9.8m/s² .). Which of following statements is correct?

A. The acceleration of the movement of this object is equal 4.9m/s² .

B. The normal reaction R to the inclined plane is 8.48Nc

C. The acceleration of the movement of this object is equal to 4.9m/s² .

D. None of the above

The force exerted by a drop of water of pressure P=2.3 x 10⁵Pa on a glass wall of surface area S=0.0042m² is?

A 3.0L bottle contains a gas at a pressure of 20bars. What volume would the gas occupy at the same temperature if the pressure were 1.0 bar?

A medium in which the speed of light depends on the frequency of is?

A. Diffusion

B. Diffraction

C.Dispersion

D. Neutral