Acceleration: The velocity v(t) of a particle as a function of time is given by v(t) = (2.3 m/s) + (4.1 m/s2)t - (6.2 m/s3)t2. What is the average acceleration of the particle between t = 1.0 s and t = 2.0 s?
A. -13 m/s2
B. -15 m/s2
C. 13 m/s2
D. 15 m/s2
E. 0 m/s2
Answer: B
You might also like to view...
Which of the following is most toxic per gram?
A. arsenic B. Botox C. water D. plutonium
An airplane in a wide sweeping "outside" loop can create zero gees inside the aircraft cabin. What must be the radius of curvature of the flight path for an aircraft moving at 150 m/s to create a condition of "weightlessness" inside the aircraft?
a. 1 150 m b. 1 800 m c. 2 300 m d. 3 600 m
A parallel plate capacitor with an air dielectric is attached to a voltage source and charged. The voltage source is removed, and then the plates are separated to double their previous distance. What happens to the energy stored by the capacitor when the plates are separated?
A. it doubles B. it quadruples C. it halves D. it is diminished by a factor of 4 E. it stays the same
Consider a heat exchanger consisting of 12.5 mm OD copper tubes in a staggered arrangement with transverse spacing 25 mm, longitudinal spacing 30 mm, and 9 tubes in the longitudinal direction. Condensing steam at 150°C flows inside the tubes. The heat exchanger is used to heat a stream of air flowing at 5 m/s from 20°C to 32°C. What is the average heat transfer coefficient and pressure drop for the tube bank?
GIVEN
Staggered copper tube bank with condensing steam inside tubes and air flowing over the outside
Tube outside diameter (D) = 12.5 mm = 0.0125 m
Transverse spacing (ST) = 25 mm = 0.025 m
Longitudinal spacing (SL) = 30 mm = 0.03 m
Number of rows of tubes (N) = 9
Steam temperature (Ts) = 150°C
Air velocity (Us) = 5 m/s
Air temperature: Ta,in = 20°C Ta,out = 32°C
FIND
(a) The average heat transfer coefficient (hc)
(b) The pressure drop (?p)
ASSUMPTIONS
Steady state
Thermal resistance of the condensing steam and the copper tube is negligible. Therefore, the tube
surface temperature = Ts
SKETCH
PROPERTIES AND CONSTANTS
Density (?) = 1.157 kg/m3
Thermal conductivity (k) = 0.0251 W/(m K)
Kinematic viscosity (?) = 15.9 × 10–6 m2/s
Prandtl number (Pr) = 0.71
Specific heat (c) = 1012 J/(kg K)
At the tube temperature of 150°C: Prs = 0.71