In the afternoon, the decibel level of a busy freeway is 85 dB with 90 cars passing a given point every minute. Late at night, the traffic flow is only 8 cars per minute. What is the late-night decibel level?

75.45db

Explanation:

Sound intensity changes on a logarithmal basis, this applies for frequency, power etc

I.e number of decibel change dB is;

db change = 10log(p2/p1)

Therefore for intensity change from 90cars/min to 8 cars/min

db change = 10log(8/90) = - 10.55db

Therefore late night decibel level becomes;

85 - 10.55 = 75.45db

a small object of mass 3.66 g and charge -17.6 µc is suspended motionless above the ground when immersed in a uniform electric field perpendicular to the ground. what are the magnitude and direction of the electric field?

force is based upon mass and acceleration.the statement is not always true.

it can be explained from newton's second law of motion.

as per newton's second law of motion the rate of change of momentum is directly proportional to the applied force and takes place along the direction of force.

mathematically it can be written as -

                                              ⇒      

here   k is the proportionality constant whose value is 1.

                                                            [a is the acceleration=dv/dt]

hence we see that force not only depends on mass and acceleration but also on velocity and rate of change of mass. force f will depend on mass and acceleration only when mass is constant.

hence the statement that force is based upon mass and acceleration is false.