Molecular Physics | Thermodynamics Answers

A steel rod of length 2000cm and uniform cross sectional area 3×10^3cm2 at 28°C. Find the change in length and the force due to exerted by the rod

(Linear expansivity of steel=1.2×10^-5/K

Young's modulus of steel = 2.0×10^7/N/cm2

A pipeline 250 mm diameter and 1580 m long has upward slopes of 1 in 200 for the first 1 km length and 1 in 100 for the remaining length. The pressures at the upper end and lower end of the pipeline are 107.91 kPa and 53.95 kPa, respectively. Determine the discharge through the pipe. Given, friction factor = 0.032.

The dung beetle is known as one of the strongest animals for its size, often forming balls of dung up to 10 times their own mass and rolling them to locations where they can be buried and stored as food. A typical dung ball formed by the species K. nigroaeneus has a radius of 1.85 cm and is rolled by the beetle at 6.20 cm/s.

(a) What is the rolling ball's angular speed (in rad/s)?

__ rad/s

(b) How many full revolutions are required if the beetle rolls the ball a distance of 1.35 m?

__ rev

A comet has a period of 80.8 years and moves in an elliptical orbit in which its perihelion (closest approach to the Sun) is 0.670 AU. Find the semimajor axis of the comet and an estimate of the comet's maximum distance from the Sun, both in astronomical units.

(a) the semimajor axis of the comet (in AU)

__ AU

(b) an estimate of the comet's maximum distance (in AU) from the Sun

 ___AU

(a) Find the magnitude of the gravitational force (in N) between a planet with mass 8.25 ✕ 10²⁴ kg and its moon, with mass 2.30 ✕ 10²² kg, if the average distance between their centers is 2.30 ✕ 10⁸ m.

___N

(b) What is the moon's acceleration (in m/s²) toward the planet? (Enter the magnitude.)

___ m/s²

A 42.0-kg child takes a ride on a Ferris wheel that rotates four times each minute and has a diameter of 26.0 m.

(a) What is the centripetal acceleration of the child?

magnitude___ m/s²

(b) What force (magnitude and direction) does the seat exert on the child at the lowest point of the ride? magnitude ___ N

(c) What force does the seat exert on the child at the highest point of the ride?magnitude___  N

(d) What force does the seat exert on the child when the child is halfway between the top and bottom? (Assume the Ferris wheel is rotating clockwise and the child is moving upward.)

magnitude ___ N

direction___  °counter-clockwise from the horizontal

A sample of blood is placed in a centrifuge of radius 16.0 cm. The mass of a red blood cell is 3.0 ✕ 10⁻¹⁶ kg, and the magnitude of the force acting on it as it settles out of the plasma is 4.0 ✕ 10⁻¹¹ N. At how many revolutions per second should the centrifuge be operated?

__ rev/s

A 38.0-kg child swings in a swing supported by two chains, each 2.90 m long. The tension in each chain at the lowest point is 436 N.

(a) Find the child's speed at the lowest point.

__ m/s

(b) Find the force exerted by the seat on the child at the lowest point. (Ignore the mass of the seat.)

___ N (upward)

It has been suggested that rotating cylinders about 14.0 mi long and 3.94 mi in diameter be placed in space and used as colonies. What angular speed must such a cylinder have so that the centripetal acceleration at its surface equals the free-fall acceleration on Earth?

___rad/s