Two skaters, both of mass 75.0 kg, are on skates on a frictionless ice pond. One skater throws a 0.40-kg ball at 6.0 m/s to his friend, who catches it and throws it back at 6.0 m/s. When the first skater has caught the returned ball, what is the velocity of each of the two skaters?
a. 0.031 m/s, moving apart
b. 0.063 m/s, moving apart
c. 0.031 m/s, moving towards each other
d. 0.063 m/s, moving towards each other
e. 12 m/s, moving apart
b
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As shown in the diagram, you've just shined a flash light toward Al, so from your point of view the light is moving to the right at speed c. Al is moving away from you to the right at speed 0.9c. According to Al, what is the light doing?
A) moving to the right at speed c B) gradually catching up to him at speed 0.1c C) moving to the right at speed 1.9c D) moving to the left at 0.1c
Three point charges are positioned on the x axis. If the charges and corresponding positions are +32 ?C at x = 0, +20 ?C at x = 40 cm, and ?60 ?C at x = 60 cm, what is the magnitude of the electrostatic force on the +32-?C charge?
a. 84 N b. 12 N c. 36 N d. 50 N e. 48 N
A heat conducting rod, 0.90 m long, is made of an aluminum section that is 0.10 m long, and a copper section that is long
Both sections have cross-sectional areas of The aluminum end is maintained at a temperature of and the copper end is at The thermal conductivity of aluminum is 205 W/m ? K and of copper is 385 W/m ? K. Steady state has been reached, and no heat is lost through the well-insulated sides of the rod. The temperature of the aluminum-copper junction in the rod is closest to A) 61°C. B) 58°C. C) 56°C. D) 54°C. E) 52°C.
A steel bolt (area 5 130 mm2, Es 5 210 GPa) is enclosed by a copper tube (length 5 0.5 m, area 5 400 mm2, Ec 5 110 GPa) and the end nut is turned until it is just snug. The pitch of the bolt threads is 1.25 mm. The bolt is now tightened by a quarter turn of the nut. The resulting stress in the bolt is approximately:
(A) 56 MPa
(B) 62 MPa
(C) 74 MPa
(D) 81 MPa