What is the acceleration of a car that slows down from 60 m/s to 40 m/s during a period of 10 seconds

 

Acceleration is the variation of Velocity in time :

  (1)

This can be written as:

  (2)

Where:

 is the final velocity

 is the initial velocity

 is the final time

 is the initial time

   

Finally:

 

The negative sign means the car is desaccelerating

A sphere is charged with electrons to −9 × 10−6 C. The value given is the total charge of all the electrons present in the sphere. To calculate the number of electrons in the sphere, we divide the the total charge with the charge of one electron.

N = 9 × 10−6 C / 1.6 × 10−19 C
N = 5.6 x 10^13