An object moves 20 m east in 30 s and then returns to its starting point taking an additional 50 s. If west is chosen as the positive direction, what is the sign associated with the average velocity of the object?
a. +
c. 0 (no sign)
b. -
d. any of the above
C
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A 230000 V-rms powerline carries an average power Pavg = 250 MW a distance of 200 km. If the total resistance of the cables is 10 ohms, what is the resistive power loss?
a. 1.0 MW b. 2.5 MW c. 5.4 MW d. 12 MW e. 10 kW
A star's size stabilizes when
A) thermal pressure and gravitational attraction balance each other. B) the star's gravitational attraction is balanced by the gravitational attraction to neighboring stars. C) the star first ignites. D) it reaches temperatures of about 3 million K.
The condition for total internal reflection can be predicted from Snell's law since
A) the index of refraction of glass is about 1.5. B) the index of refraction of plastic is about 1.5. C) the value of tangent can be 1.0. D) the maximum value of the sine is 1.0. E) the maximum value of the sine is 1.5.
A car originally traveling at 30 m/s manages to brake for 5.0 seconds while traveling 125 m downhill. At that point the brakes fail. After an additional 5.0 seconds it travels an additional 150 m down the hill. What was the acceleration of the car after the brakes failed?