Question

Police car is chasing a speed limit violator car with a Doppler radar installed on the roof. Suppose the speed of sound is 300 m/s. When the police car has a velocity v = 10 m/s in the lab frame, it sends a 30 kHz frequency signal.

3.1 [1pt] If the violator is moving at 20 m/s, what would be the frequency of the radar signal if received by an instrument installed at the violator car?

ANSWER

3.2 [1pt] If the police car detected a returning signal at 29 kHz (after bouncing off the violator’s car), what is the velocity of the violator? Describe the situation in words.

ANSWER

Suppose we took a parallel plates capacitor: the plates have area 1 by 1 meter and they are separated by 1 cm with vacuum.

3.3 [1pt] What would be the force between the two plates if we deposit a charge of 1 Coulomb.

ANSWER

3.4 [1pt] How will the force in 3.3 change if we fill the space between the capacitors plate with a silicon, which has a dielectric relative permittivity of 10.

ANSWER

Answer 1