A un automóvil de 15680 que se mueve a una velocidad de 20 m / s se le aplica una fuerza de 6,4 · 10 2N hasta que se Detiene. A. ¿Cuál es la masa del auto? B. ¿Cuál era su cantidad de movimiento ( momento) inicial?Ç c. ¿Cuál fue el cambio en momento del auto? D. ¿Cuánto tiempo se aplicó la fuerza? Sol:a)1,6·103Kg b)3,2·104 kgm/s C)3,2·104 kgm/s D)50s

A)  m = 1600 kg ,  B)  p = 3.2 10⁴ kg m / s , C)  Δp = - 3.2 10⁴ kg m / s

D)  t = 51.6 s

Explanation:

A) They indicate the weight of the vehicle W = 15680 N

weight is the attraction of the earth on a body

          W = m g

           m = W / g

           m = 15680 / 9.8

           m = 1600 kg

B) The momentum is defined by

           p = m v

           p = 1600 20

           p = 3.2 10⁴ kg m / s

C) the moment change is

           Δp = p_{f} -p₀

as the vehicle stops the final speed is zero and therefore the moment is zero

           ΔP = 0 - p₀

            Δp = - 3.2 10⁴ kg m / s

D) Let's use Newton's second law

            F = m a

            a = F / m

            a = 6.2 102/1600

            a = 0.3875 m / s²

Now we can use kinematics, note that as the vehicle stops, the relationship must be opposite to the speed

            v = v₀ - a t

            v = 0

             0 = v₀ - a t

             t = v₀ / a

             t = 20 / 0.3875

             t = 51.6 s

the answer is b, have negligible mass

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.