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A particle's acceleration is given by a = (6t − 18) m/s2, and its initial velocity is V0 = 24 m/s (at t=0). Find a) the velocity V of the particle at any time t, and b) the values of t at maximum disp

Physics

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3 parts
a

V(t)=3t2−18t+24 m/sV(t) = 3t^2 - 18t + 24 \text{ m/s}

b

t=2 s and t=4 st=2 \text{ s and } t=4 \text{ s}

c

12 m12 \text{ m}

Step-by-step solution

9 steps

A particle's acceleration is given by a=(6t−18) m/s2a = (6t - 18) \text{ m/s}^2, and its initial velocity is V0=24 m/sV_0 = 24 \text{ m/s} (at t=0t=0).

Part a· 3 steps

The velocity (VV) of the particle at any time (tt).

  1. Integrate the acceleration function to find the velocity function.

    Velocity V(t)V(t) is the integral of acceleration a(t)a(t) with respect to time tt.

    V(t)=∫a(t) dtV(t) = \int a(t)\,dt V(t)=∫(6t−18) dtV(t) = \int (6t - 18)\,dt V(t)=6t22−18t+CV(t) = \frac{6t^2}{2} - 18t + C V(t)=3t2−18t+CV(t) = 3t^2 - 18t + C
  2. Use the initial condition to find the constant of integration CC.

    Given that the initial velocity is 24 m/s24 \text{ m/s} at t=0t=0:

    V(0)=3(0)2−18(0)+C=24V(0) = 3(0)^2 - 18(0) + C = 24 C=24C = 24
  3. Write the complete velocity function.

    V(t)=3t2−18t+24 m/sV(t) = 3t^2 - 18t + 24 \text{ m/s}

    The velocity of the particle at any time tt is V(t)=3t2−18t+24 m/s\boxed{V(t) = 3t^2 - 18t + 24 \text{ m/s}}.

Part b

t=2 s and t=4 st=2 \text{ s and } t=4 \text{ s}

The values of tt at maximum displacement of the particle.

  1. Maximum displacement occurs when the velocity of the particle is zero, as the particle momentarily stops before changing direction.

    Set V(t)=0V(t) = 0:

    3t2−18t+24=03t^2 - 18t + 24 = 0
  2. Solve the quadratic equation for tt.

    Divide the entire equation by 3:

    t2−6t+8=0t^2 - 6t + 8 = 0

    Factor the quadratic equation:

    (t−2)(t−4)=0(t-2)(t-4) = 0

    This gives two possible values for tt:

    t−2=0  ⟹  t=2 st-2 = 0 \implies t = 2 \text{ s} t−4=0  ⟹  t=4 st-4 = 0 \implies t = 4 \text{ s}

    The values of tt at maximum displacement are t=2 s and t=4 s\boxed{t=2 \text{ s and } t=4 \text{ s}}.

Part c

12 m12 \text{ m}

The distance covered by the particle between t=1t=1 second and t=5t=5 seconds.

  1. Determine the displacement function s(t)s(t) by integrating the velocity function.

    s(t)=∫V(t) dts(t) = \int V(t)\,dt s(t)=∫(3t2−18t+24) dts(t) = \int (3t^2 - 18t + 24)\,dt s(t)=t3−9t2+24t+D0s(t) = t^3 - 9t^2 + 24t + D_0

    For calculating distance, the constant D0D_0 is not needed as it cancels out in differences.

  2. Identify the intervals where the velocity changes sign.

    From part (b), we know V(t)=0V(t)=0 at t=2t=2 s and t=4t=4 s. These are the points where the particle changes direction.
    We need to calculate the distance in the intervals [1,2][1, 2], [2,4][2, 4], and [4,5][4, 5].

  3. Calculate the displacement in each interval and take the absolute value to find the distance.

    • For the interval [1,2][1, 2]:
    s(2)−s(1)=(23−9(2)2+24(2))−(13−9(1)2+24(1))s(2) - s(1) = (2^3 - 9(2)^2 + 24(2)) - (1^3 - 9(1)^2 + 24(1)) s(2)−s(1)=(8−36+48)−(1−9+24)s(2) - s(1) = (8 - 36 + 48) - (1 - 9 + 24) s(2)−s(1)=20−16=4 ms(2) - s(1) = 20 - 16 = 4 \text{ m}

    Distance for [1,2][1, 2] is ∣4∣=4 m|4| = 4 \text{ m}.

    • For the interval [2,4][2, 4]:
    s(4)−s(2)=(43−9(4)2+24(4))−(23−9(2)2+24(2))s(4) - s(2) = (4^3 - 9(4)^2 + 24(4)) - (2^3 - 9(2)^2 + 24(2)) s(4)−s(2)=(64−144+96)−(8−36+48)s(4) - s(2) = (64 - 144 + 96) - (8 - 36 + 48) s(4)−s(2)=16−20=−4 ms(4) - s(2) = 16 - 20 = -4 \text{ m}

    Distance for [2,4][2, 4] is ∣−4∣=4 m|-4| = 4 \text{ m}.

    • For the interval [4,5][4, 5]:
    s(5)−s(4)=(53−9(5)2+24(5))−(43−9(4)2+24(4))s(5) - s(4) = (5^3 - 9(5)^2 + 24(5)) - (4^3 - 9(4)^2 + 24(4)) s(5)−s(4)=(125−225+120)−(64−144+96)s(5) - s(4) = (125 - 225 + 120) - (64 - 144 + 96) s(5)−s(4)=20−16=4 ms(5) - s(4) = 20 - 16 = 4 \text{ m}

    Distance for [4,5][4, 5] is ∣4∣=4 m|4| = 4 \text{ m}.

  4. Sum the distances from each interval to find the total distance covered.

    Total distance =4 m+4 m+4 m=12 m= 4 \text{ m} + 4 \text{ m} + 4 \text{ m} = 12 \text{ m}.
    The distance covered by the particle between t=1t=1 second and t=5t=5 seconds is 12 m\boxed{12 \text{ m}}.

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