Equilibrium: A 3.00-m-long ladder, weighing 200 N, leans against a smooth vertical wall with its base on a horizontal rough floor, a distance of 1.00 m away from the wall. The ladder is not completely uniform, so its center of gravity is 1.20 m from its base. What force of friction must the floor exert on the base of the ladder to prevent the ladder from sliding down?
A. 93.3 N
B. 130 N
C. 28.3 N
D. 102 N
E. 150 N
Answer: C
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Intensity: The rate of energy flow per unit area of a sinusoidal electromagnetic wave has an average value of 0.601 W/m2. What is the maximum value of the magnetic field in the wave? (c = 3.00 × 108 m/s, ?0 = 4? × 10-7 T ? m/A, ?0 = 8.85 × 10-12 C2/N ? m2)
A. 7.09 × 10-8 T B. 5.02 × 10-8 T C. 3.55 × 10-8 T D. 9.81 × 10-8 T E. 1.42 × 10-7 T
How will the Kepler mission (scheduled for 2008 launch) look for planets around other stars?
A) It will look for Doppler shifts in stellar spectra. B) It will be sufficiently powerful to take low-resolution photographs of planets orbiting nearby stars. C) It will look for slight back and forth shifts in a star's position in our sky. D) It will look for slight changes in a star's brightness that repeat at regular intervals.
Asteroids are sometimes referred to as ______________ planets
Fill in the blank(s) with correct word
The magnetic field in a superconducting solenoid is 3.0 T. How much energy per unit volume is stored in the solenoid, in J/m3? m0 = 4p × 10^-7 T × A/m