A1811kg car speeds up from rest when a traffic light turns green until it reaches a speed of 23m/s. how much work was done on the car by friction?

The work done by the frictional force, W = 612565.32 J

Explanation:

Given data,

The mass of the car, m = 1811 kg

The initial velocity of the car, u = 0 m/s

The final velocity of the car, v = 23 m/s

Let the time period of the car be, t = 3 s

The acceleration of the car,

                              a = (v-u) /t

                                 = (23 - 0)/ 3

                                = 7.67 m/s²

The normal force acting on the car,

                         F = mg

                             = 1811 kg x 9.8 m/s²

                              = 17747.8 N

The displacement of the car,

                             s = ut + ½ at²

                                 = 0 + ½ x 7.67 x 3²

                                 = 54.52 m

The work done by the frictional force,

                              W = F · S

                              W = 17747.8 N x 54.52 m

                                   = 612565.32 J

Hence, the work done by the frictional force, W = 612565.32 J

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.