One 20-year-old twin brother takes a space trip with a speed of 0.80c for 30 years according to a clock on his spaceship. At the end of this trip, what are (a) his own age and (b) the age of his Earth-based twin brother?
A) (a) 20 y (b) 30 y
B) (a) 30 y (b) 50 y
C) (a) 50 y (b) 70 y
D) (a) 70 y (b) 90 y
C
You might also like to view...
To measure the mass flow rate of a fluid in a laminar flow through a circular pipe, a hot wire type velocity meter is placed in the center of the pipe. Assuming that the measuring station is far from the entrance of the pipe, the velocity distribution is parabolic where Umax is the centerline velocity (r = 0), r is the radial distance from the pipe centerline, D is the pipe diameter.
(a) Derive an expression for the average fluid velocity at the cross-section in terms of
Umax and D.
(b) Obtain an expression for the mass flow rate.
(c) If the fluid is mercury at 30°C, D = 10 cm, and the measured value of Umax is 0.2
cm/s, calculate the mass flow rate from the measurement.
GIVEN
• Fully developed flow of mercury through a circular pipe
• Parabolic velocity distribution: u(r)/Umax = 1 – (2r/D)2
• Mercury temperature (T) = 30°C
• Pipe diameter (D) = 10 cm = 0.1 m
• Measured center velocity (Umax) = 0.2 cm/s = 0.002 m/s
FIND (a) An expression for the average fluid velocity (u )
(b) An expression for the mass flow rate (m )
c) The value of the mass flow rate (m )
SKETCH
The following data refer to a car traveling west: t (s) 0 1 2 3 4 -------------------------- v (m/s) 30 25 20 15 10 Find the magnitude and direction of the acceleration
If I = 2.0 A in the circuit segment shown below, what is the potential difference VB ? VA?
a.
+10 V
b.
?20 V
c.
?10 V
d.
+20 V
e.
+30 V
A horizontal wire of length 3.6 m carries a current of 6.0 A and is oriented so that the current direction is 50° S of W. The Earth's magnetic field is due north at this point and has a strength of 0.14 × 10^-4 T. What is the direction of the force on the wire?
a. 40° S of E c. toward the Earth's surface b. out of the Earth's surface d. due east