Molecular Physics | Thermodynamics Answers

A student of mass 59.4 kg, starting at rest, slides down a slide 24.2 m long, tilted at an angle of 20.1° with respect to the horizontal. If the coefficient of kinetic friction between the student and the slide is 0.108, find the force of kinetic friction, the acceleration, and the speed she is traveling when she reaches the bottom of the slide. (Enter the magnitudes.)

(a) the force of kinetic friction (in N) __ N

(b) the acceleration (in m/s²) ___m/s²

(c) the speed she is traveling (in m/s) ___ m/s

A block of mass m₁ = 20.4 kg is on a frictionless table to the left of the second block of mass m₂ = 23.7 kg, attached by a horizontal string (see the figure below).

(a) If a horizontal force of 1.13 ✕ 10² N is exerted on the block m₂ in the positive x-direction, use the system approach to find the acceleration (in m/s²) of the two blocks.

___ m/s²

(b) What is the tension (in N) in the string connecting the blocks?

____ N

Air has a velocity of 1000 km/h at a pressure of 9.81 kN/m2 in vacuum

and a temperature of 47°C. Compute its stagnation properties and the local Mach number. Take

atmospheric pressure = 98.1 kN/m2, R = 287 J/kg K and γ = 1.4.

What would be the compressibility correction factor for a pitot-static tube to measure the

velocity at a Mach number of 0.8

Air at a pressure of 220 kN/m2 and temperature 27°C is moving at a

velocity of 200 m/s. Calculate the stagnation pressure if

(i) Compressibility is neglected ;

(ii) Compressibility is accounted for.

In aircraft flying at an altitude where the pressure was 35 kPa and

temperature – 38°C, stagnation pressure measured was 65.4 kPa. Calculate the speed of the

aircraft. Take molecular weight of air as 28

A rabbit is moving in the negative x-direction at 1.10 m/s when it spots a predator and accelerates to a velocity of 11.5 m/s along the positive y-axis, all in 1.40 s. Determine the x-component and the y-component of the rabbit's acceleration. (Enter your answers in m/s². Indicate the direction with the signs of your answers.)

(a)

x-component

 m/s²

(b)

y-component

 m/s²

A record of travel along a straight path is as follows:

1. Start from rest with constant acceleration of 2.40 m/s² for 16.0 s.

2. Maintain a constant velocity for the next 1.20 min.

3. Apply a constant negative acceleration of −9.29 m/s² for 4.13 s.

(a) What was the total displacement for the trip?

(b) What were the average speeds for legs 1, 2, and 3 of the trip, as well as for the complete trip?leg 1     

 m/sleg 3     

 m/scomplete trip     

 m/s

Below is a 𝑇𝑉 diagram of a reversible process of a monatomic ideal gas with 𝑛 moles such that 𝑛𝑅 = 2.00 J K −1 . The process traces the curve 𝑇 = (400 K m−3 ) 𝑉 − (100 K m−6 ) 𝑉 2 starting at state 𝑎 with 𝑉𝑎 = 3.00 m3 and ending at state 𝑏 with with 𝑉𝑏 = 1.00 m3.Calculate, for this process (ensure that signed values have the correct sign): (a) Pressures 𝑃𝑎 and 𝑃𝑏 at the endpoints, in Pa (b) Change in internal energy, ∆𝑈, in J (c) Work 𝑊 done by the gas, in J (d) Heat 𝑄 added to the gas, in J (e) Entropy change Δ𝑆 of the gas, in J K.

why entropy is constant in adiabatic process

5. A steady state, steady flow compressor draws in 240 liters per second of air whose density is 1.26

kg m /m 3 and discharges it with a density of 4.9 kg m /m 3 . At suction P 1 = 104 kPaa; at discharge, P 2 = 551

kPaa. The increase of specific internal energy is 78.5 kJ/kg m and the heat from the air by cooling is 30

kJ/kg m . Neglecting the change in potential and kinetic energies, determine the work in kJ/min.