Molecular Physics | Thermodynamics Answers

If a ½ hp pump runs for 21 minutes, what is the energy used in kW-hr?

The heart consumes 350 kJ of energy per day. What is heart efficiency if it strikes 62 beats per minute and makes a work of 1.1 J per one stroke?

The power of the heat fan is 2.00 kW. How much coal should be burned per hour to produce the corresponding heat when the calorific value of the coal is 28.4 MJ/kg?

Consider the plane makes intercepts of 2 A , 3 A , 4 A on the coordinate axis of the crystal

with a: b: c = 4: 3 : 2. The crystal is orthorho1nbic crystal. Calculate the miller indices of

the given plane of the crystal.

A 2.30 kg hoop of radius 0.160 m is released from rest at point A in the figure below, its center of gravity a distance of 1.80 m above the ground. The hoop rolls without slipping to the bottom of an incline and back up to point B where it is launched vertically into the air. The hoop then rises to its maximum height h_max at point C.

(a)

At point B, find the hoop's translational speed v_B (in m/s).

___ m/s

(b)

At point B, find the hoop's rotational speed 𝜔_B (in rad/s).

___ rad/s

(c)

At point C, find the hoop's rotational speed 𝜔_C (in rad/s).

___ rad/s

(d)

At point C, find the maximum height h_max of the hoop's center of gravity (in m).

 ___ m

A car is designed to get its energy from a rotating flywheel in the shape of a uniform, solid disk of radius 0.650 m and mass 600 kg. Before a trip, the flywheel is attached to an electric motor, which brings the flywheel's rotational speed up to 4.90 ✕ 10³ rev/min.

(a)

Find the kinetic energy stored in the flywheel (in J).

 __J

(b)

If the flywheel is to supply energy to the car as a 11.0 hp motor would, find the length of time in hours the car could run before the flywheel would have to be brought back up to speed.

__ h

The uniform thin rod in the figure below has mass M = 2.00 kg and length L = 3.73 m and is free to rotate on a frictionless pin. At the instant the rod is released from rest in the horizontal position, find the magnitude of the rod's angular acceleration, the tangential acceleration of the rod's center of mass, and the tangential acceleration of the rod's free end.

(a)

the rod's angular acceleration (in rad/s²)

___ rad/s²

(b)

the tangential acceleration of the rod's center of mass (in m/s²)

___ m/s²

(c)

the tangential acceleration of the rod's free end (in m/s²)

___ m/s²

A 520-N uniform rectangular sign 4.00 m wide and 3.00 m high is suspended from a horizontal, 6.00-m-long, uniform, 150-N rod as indicated in the figure below. The left end of the rod is supported by a hinge and the right end is supported by a thin cable making a 30.0° angle with the vertical. (Assume the cable is connected to the very end of the 6.00-m-long rod, and that there are 2.00 m separating the wall from the sign.)

(a) Find the (magnitude of the) tension T in the cable.

__ N

(b) Find the horizontal and vertical components of the force exerted on the left end of the rod by the hinge. (Take up and to the right to be the positive directions. Indicate the direction with the sign of your answer.)

horizontal component __ N

vertical component __ N

Consider the following mass distribution where the x- and y-coordinates are given in meters: 5.0 kg at (0.0, 0.0) m, 2.9 kg at (0.0, 4.8) m, and 4.0 kg at (2.7, 0.0) m. Where should the fourth object of 9.4 kg be placed so that the center of gravity of the four-object arrangement will be at (0.0, 0.0) m?

x = ___  m

y = ___ m

A mechanic applies a torque to a nut with a wrench 0.250 m long. Because of the cramped space, he must exert a force upward at an angle of 50.0° with respect to a line from the nut through the end of the wrench. If the force he exerts has magnitude 40.0 N, what magnitude torque (in N · m) does he apply to the nut? (Assume that the force is applied at the end of the wrench.)

___ N · m