According to the special theory of relativity, which of the following happens to the length of an object, measured in the dimension parallel to the motion of its inertial frame of reference, as the velocity of this frame increases with respect to a stationary observer?
a. length increases
b. length decreases
c. length remains constant
d. length vanishes to zero when velocity equals half speed of light
b
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A very thin uniform rod, 2.40 m long and of weight 135 N, has a frictionless hinge at its lower end
It starts out vertically from rest and falls, pivoting about the hinge. Just as it has rotated through an angle of 55.0°, what is the downward acceleration of the end farthest from the hinge? A) 5.02 m/s2 B) 8.03 m/s2 C) 9.80 m/s2 D) 12.0 m/s2 E) 19.6 m/s2
A 4.0 kg box of fruit slides 8.0 m down a ramp, inclined at 30.° from the horizontal. If the box slides at a constant velocity of 5.0 m/s, the work done by gravity is
A) +78. J. B) 0.16 kJ. C) -78. J. D) zero. E) -0.16 kJ.
Human activities that warm the Earth's atmosphere are caused by energy
A) production. B) consumption. C) both of these D) none of the above
A 1500 kg point mass (
A) and a 1200 kg point mass (B) are held in place 1.00 m apart on a frictionless table. A third point mass is placed between the masses 20.0 cm from B along the line connecting A and B and then released. Find the magnitude and direction (toward A or toward B) of the acceleration of the third mass just after it is released.