An object is moving along the x-axis. At t = 0 it has velocity v0x = 20.0 m/s. Starting at time t = 0 it has acceleration ax = - Ct, where C has units of m/s3. (a) What is the value of C if the object stops in 8.00 s after t = 0? (b) For the value of C calculated in part (a), how far does the object travel during the 8.00 s?

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Answer:

Explanation:

Given

At [tex]t=0[/tex] velocity [tex]v_{0x}=20\ m/s[/tex]

at this instant acceleration [tex]a_x=-Ct[/tex]

[tex]a=\frac{\mathrm{d} v}{\mathrm{d} t}=-Ct[/tex]

[tex]\int_{20}^{0}dv=\int_{0}^{8}-Ctdt[/tex]

[tex]\int_{0}^{20}dv=\int_{0}^{8}Ctdt[/tex]

[tex]C=\frac{5}{8}[/tex]

(b)Distance traveled in 8 s

[tex]a=\frac{\mathrm{d} v}{\mathrm{d} t}=-Ct[/tex]

[tex]\int_{20}^{v}dv=\int_{0}^{t}-Ctdt[/tex]

[tex]v-20=-\frac{Ct^2}{2}[/tex]

[tex]v=20-\frac{Ct^2}{2}[/tex]

[tex]v=\frac{\mathrm{d} x}{\mathrm{d} t}[/tex]

[tex]\int_{0}^{8}vdt=\int_{0}^{x}dx[/tex]

[tex]\int_{0}^{8}20-\frac{Ct^2}{2}dt=\int_{0}^{x}dx[/tex]

[tex]x=20t|_{0}^{8}-\frac{C}{6}t^3|_{0}^{8}[/tex]

here value of [tex]C=\frac{5}{8}[/tex]

[tex]x=20\times 8-\frac{0.625}{6}\times 8^3[/tex]

[tex]x=106.67\ m[/tex]

The value of C if the object stops in 8.00 s is 0.625 m/s³.

The distance traveled by the object before stopping in 8 seconds is 40 m.

The given parameters;

  • initial velocity, [tex]v_0[/tex] = 20.0 m/s
  • initial time of motion, t = 0
  • acceleration of the object, a = -Ct

The value of C is determined by using velocity equation as shown below;

[tex]\frac{dv}{dt} = -Ct\\\\dv = -Ctdt\\\\\int\limits^v_{v_0} \, dv = -\int\limits^t_{t_0} \, Ct \\\\v-v_0= -C[\frac{t^2}{2} ]^t_0\\\\v-v_0 = - \frac{1}{2} Ct^2\\\\0 - 20 = - \frac{1}{2}C(8)^2\\\\-20 = -32 C\\\\C = \frac{20}{32} = 0.625 \ m/s^3[/tex]

The acceleration of the object during 8 seconds is calculated as follows;

a = -Ct

a = -0.625(8)

a = -5 m/s²

The distance traveled by the object before stopping in 8 seconds is calculated as follows;

[tex]v^2 = u^2 + 2as\\\\0 = 20^2 + 2(-5)s\\\\0 = 400 - 10s\\\\10s = 400 \\\\s = \frac{400}{10} \\\\s = 40 \ m[/tex]

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