The acceleration of the car is 6.86 m/s² and the time taken for the car to stop is 3.64 s.
The given parameters;
- mass of the car, m = 1400 kg
- Initial velocity of the car, u = 25 m/s
- coefficient of kinetic friction, μ = 0.7
The acceleration of the car is calculated as follows;
a = μg
a = 0.7 x 9.8
a = 6.86 m/s²
The time taken for the car to stop is calculated by using Newton's second law of motion;
F = ma

Thus, the acceleration of the car is 6.86 m/s² and the time taken for the car to stop is 3.64 s.
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The force acting on his feet.
Frequency = (speed) / (wavelength) = 20 / 0.5 = 40 per second = 40 Hz.
When rubbing two insulators together, electrons from one insulator will be transfered to the other. so the insulator that has just received electrons now has a negative charge as it has received more electrons (making it more negative) the insulator that has just lost electrons has just become positively charged. NEVER SAY THAT PROTONS HAVE BEEN TRANSEFERD.... EVER. ONLY ELECTORNS ARE TRANSFERED.