Exercises and problems in Physics
New experimental problem:
M. 220. Prepare an air vane
supported in good bearings using paper cones or table tennis balls cut in
two. Measure how the number of revolutions per minute of the vane depends on
the speed of the air current (wind). Can we deduce the coefficient of air
resistance for the concave and the convex side using the measurement data?
P. 3384. Water is poured into a quadrangular vessel. What
is the height of the vessel if the force exerted onto each side is greater than
the weight of the water?
P. 3385. An aluminium cube with 2 dm sides and
2700 kg/m3 density is fastened to one end
of a 3 m long chain lying on a table, each metre of which has a mass of
1 kg. The cube is lifted at a uniform speed of 0.5 m/s. What is the
change of the potential energy after a) 5 seconds, b) 10 seconds
P. 3386. A 3 litre container with insulated walls is
divided into two equal parts by a rigid, heat conducting wall. There is oxygen
with a pressure of 105 Pa and a
temperature of 300 K in both parts: diatomic (O2) on the left side and triatomic (O3), i.e. ozone on the right. After some time, ozone passes
into diatomic oxygen in such a way that two ozone molecules transform into
three O2 molecules: 2O33O2. a) What is the number of oxygen molecules in
each part? b) What are the pressure and temperature in each part when
thermal equilibrium is reached if 2.4.10-19 J of energy are released during the
transformation of each ozone molecule? (Consider the gases O3 and O2 as ideal gases of
respectively 6 and 5 degrees of freedom.)
P. 3387. Why do children usually sweat less than adults
when performing sports?
P. 3388. A body of mass m is slid upwards on a lath
of inclination in a uniform
motion. Determine the magnitude and the direction of the minimum force required
for the sliding. The coefficient of friction is .
P. 3389. Two bodies of
respective masses m and M are joined to each other by a
weightless thread flung over a pulley of negligible mass. The two bodies are
held in the position shown in the figure and released at a given moment. Mass
M is much (e.g. a thousand times) greater than mass m. Friction
between the body of mass m and the table is negligible. Is the body of
mass m separated from the table right after the two bodies are released?
P. 3390. What should the
capacitance C in the circuit shown in the figure be so that the energy
accumulating in it is maximum? What is this maximum amount of energy?
P. 3391. An electron beam
reaches the d=4 cm wide homogeneous magnetic field of induction
B=0.02 T shown in the figure at an angle of incidence =30o, at right
angles to vector B. a) Slow or fast particles can get through the
magnetic field? b) At what pd. should the elctrons be accelerated so
that they are ``reflected'' from the magnetic field?
P. 3392. In the series
RLC circuit shown in the figure, the bulb shines. When the coil is
short-circuited the light emission of the bulb does not change. How does it
change when the capacitor is short-circuited?
P. 3393. A regular
tetrahedron is made of a homogeneous resistance wire of uniform
cross-section. Current I is conducted to vertex A through a long,
straight piece of wire directed toward centre O of the tetrahedron, and
it is conducted away from vertex B in the same fashion. What are the
magnitude and the direction of the magnetic induction vector at the centre of
Send your solutions to the following address:
KöMaL Szerkesztőség (KöMaL feladatok),
Budapest Pf. 47. 1255, Hungary
or by e-mail to: firstname.lastname@example.org.
Deadline: 13 January 2001