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To a wave, wavelength * frequency = velocity. The speed of light in vacuum = 2.99792458e8 m/s ¡Ö 3*10^8 m/s. (a) wavelength = velocity/frequency = 3*10^8/(3*10^19) = 10^-11 m. (b) wavelength = 3*10^8/(7.5*10^9) = 0.04 m.
1. To balance the gravity of the 75N block, the pull force from the cable applied on it should be 75N. 2. Then the cable pulls the 150N block with a force of 75N. 3. To balance the pull force from the cable, the static friction should be 75N. 4. And the
Based on the conservation of momentum, the velocity of launcher V=vo*m/M. The kinetic energy of launcher is E=1/2*M*V^2=1/2*m/M*m*vo^2. Suppose the coefficient of friction is C. The friction F=C*M*g. The launcher is stoped, then F*x=E,then

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