Explanation :
It is given that,
Mass of the car, m = 1000 kg
Force applied by the motor, 
The static and dynamic friction coefficient is, 
Let a is the acceleration of the car. Since, the car is in motion, the coefficient of sliding friction can be used. At equilibrium,




So, the acceleration of the car is
. Hence, this is the required solution.
The correct answer would be 1.375 < t < 3 i hope this helps anyone
We know,
V= f× wavelength
10.5= f×0.15
f=10.5/0.15
f= 70 Hz
It would take at less 10 minte i guess this the right awnser