The velocity of a ball changes from ‹ 9, −6, 0 › m/s to ‹ 8.96, −6.12, 0 › m/s in 0.02 s, due to the gravitational attraction of the Earth and to air resistance. The mass of the ball is 120 grams.

(a) What is the acceleration of the ball? a with arrow = Correct: Your answer is correct. (m/s)/s

(b) What is the rate of change of momentum of the ball? dp with arrow/dt = Incorrect: Your answer is incorrect. (kg · m/s)/s

(c) What is the net force acting on the ball? F with arrownet = N

Answer :

AMB000

Answer:

a) [tex]a=(-2,-6,0)m/s^2[/tex], with a magnitude of [tex]6.3m/s^2[/tex]

b) [tex]\frac{\Delta p}{\Delta t}=(-0.24,-0.72,0)Kgm/s^2[/tex], with a magnitude of [tex]0.76Kgm/s^2[/tex]

c) [tex]F=(-0.24,-0.72,0)N[/tex], with a magnitude of [tex]0.76N[/tex]

Explanation:

We have:

[tex]v_{ix}=9m/s, v_{iy}=-6m/s, v_{iz}=0m/s\\v_{fx}=8.96m/s, v_{fy}=-6.12m/s, v_{fz}=0m/s\\t=0.02s, m=0.12Kg[/tex]

We can calculate each component of the acceleration using its definition [tex]a=\frac{\Delta v}{\Delta t}[/tex]

[tex]a_x=\frac{v_{fx}-v_{ix}}{t} = \frac{(8.96m/s)-(9m/s)}{0.02s} =-2m/s^2\\a_y=\frac{v_{fy}-v_{iy}}{t} = \frac{(-6.12m/s)-(-6m/s)}{0.02s} =-6m/s^2\\a_y=\frac{v_{fz}-v_{iz}}{t} = \frac{(0m/s)-(0m/s)}{0.02s} =0m/s^2\\[/tex]

The rate of change of momentum of the ball is [tex]\frac{\Delta p}{\Delta t} = \frac{\Delta mv}{\Delta t} = \frac{m\Delta v}{\Delta t} = ma[/tex]

So for each coordinate:

[tex]\frac{\Delta p_x}{\Delta t}=-0.24Kgm/s^2\\\frac{\Delta p_y}{\Delta t}=-0.72Kgm/s^2\\\frac{\Delta p_z}{\Delta t}=0Kgm/s^2[/tex]

And these are equal to the components of the net force since F=ma.

If magnitudes is what is asked:

[tex]a=\sqrt{a_x+a_y+a_z} =6.3m/s^2\\F=ma=\frac{\Delta p}{\Delta t}=0.76N[/tex]

(N and [tex]Kgm/s^2[/tex] are the same unit).

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