Posted: September 16th, 2017

Engineering Physics

1. An electric motor rotating a workshop grinding wheel at a rate of 125 rev/min is switched off. Assume
constant negative angular acceleration of magnitude 2.15 rads
2
. (a) How long does it take for the grinding
wheel to stop? (b) Through how many radians has the wheel turned during the interval found in (a)?
2. Find the centripetal accelerations of (a) a point on the Equator (b) at North Pole and (c) at the location of
Ada (40° N lattitude), due to the rotation of Earth about its axis.
3. In the Bohr model of the hydrogen atom, an electron (mass = 9.1μ10-31 kg) orbits a proton (mass =
1.67μ10-27 kg) at a distance of 5.3μ10-11 m. (a) What is the gravitational force exerted by the proton on the
electron? (b) If the electric force of attraction between the particles is 8.2μ10-8
N, how many revolutions per
second does the electron make? (c) What is the tangential velocity of the elctron?
4. A steel cylinder of mass 0.325 kg is tied to a string and allowed to revolve in a circle of radius 1.15 m on
a frictionless horizontal table. The other end of the string passes through a hole in the center of the table, and a
mass of 1.00 kg is tied to it. The suspended mass remains in equilibrium while the cylinder on the tabletop
revolves. (a) What is the tension in the string? (b) What is the horizontal force acting on the steel cylinder? (c)
What is the speed of the steel cy