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Relate acceleration to velocity.

Physics

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3 parts
a(i)

V=−t2+5t+2 m/sV = -t^2 + 5t + 2 \, \text{m/s}

a(ii)

8 m/s8 \, \text{m/s}

b

2.5 s2.5 \, \text{s}

18512 m or 15.42 m (to 2 d.p.)\frac{185}{12} \, \text{m} \text{ or } 15.42 \, \text{m (to 2 d.p.)}

Step-by-step solution

10 steps

Part a(i)· 4 steps

Express VV in terms of tt.

  1. Relate acceleration to velocity.

    Acceleration aa is the rate of change of velocity VV with respect to time tt.

    a=dVdta = \frac{dV}{dt}

    Given a=(5−2t) m/s2a = (5 - 2t) \, \text{m/s}^2.
    So, we have:

    dVdt=5−2t\frac{dV}{dt} = 5 - 2t
  2. Integrate the acceleration to find the velocity function.

    dV=(5−2t) dtdV = (5 - 2t) \, dt ∫dV=∫(5−2t) dt\int dV = \int (5 - 2t) \, dt V=5t−2t22+CV = 5t - \frac{2t^2}{2} + C V=5t−t2+CV = 5t - t^2 + C
  3. Use the initial condition to find the constant of integration CC.

    The initial velocity is 2 m/s2 \, \text{m/s}, which means V=2V=2 when t=0t=0.

    2=5(0)−(0)2+C2 = 5(0) - (0)^2 + C 2=C2 = C
  4. Write the expression for VV in terms of tt.

    V=5t−t2+2V = 5t - t^2 + 2

    The expression for VV in terms of tt is V=−t2+5t+2 m/s\boxed{V = -t^2 + 5t + 2 \, \text{m/s}}.

Part a(ii)

8 m/s8 \, \text{m/s}

Determine the velocity of the particle at the beginning of the third second.

  1. Identify the time value for the beginning of the third second.

    The beginning of the third second corresponds to t=2t=2 seconds.

  2. Substitute t=2t=2 into the velocity equation found in part (a)(i).

    V=−(2)2+5(2)+2V = -(2)^2 + 5(2) + 2 V=−4+10+2V = -4 + 10 + 2 V=6+2V = 6 + 2 V=8 m/sV = 8 \, \text{m/s}

    The velocity at the beginning of the third second is 8 m/s\boxed{8 \, \text{m/s}}.

Part b

2.5 s2.5 \, \text{s}

Find the time taken by the particle to attain maximum velocity and the distance it covered to attain the maximum velocity.

  1. Find the time taken to attain maximum velocity.

    Maximum velocity occurs when the acceleration is zero (a=dVdt=0a = \frac{dV}{dt} = 0).
    Given a=5−2ta = 5 - 2t.
    Set a=0a = 0:

    5−2t=05 - 2t = 0 2t=52t = 5 t=52t = \frac{5}{2} t=2.5 st = 2.5 \, \text{s}

    The time taken to attain maximum velocity is 2.5 s\boxed{2.5 \, \text{s}}.

  2. Find the distance covered to attain the maximum velocity.

    Distance ss is the integral of velocity VV with respect to time tt.

    s=∫V dts = \int V \, dt

    Using V=−t2+5t+2V = -t^2 + 5t + 2:

    s=∫(−t2+5t+2) dts = \int (-t^2 + 5t + 2) \, dt s=−t33+5t22+2t+Ds = -\frac{t^3}{3} + \frac{5t^2}{2} + 2t + D
  3. Use the initial condition for displacement to find the constant of integration DD.

    Assume that at t=0t=0, the displacement s=0s=0.

    0=−(0)33+5(0)22+2(0)+D0 = -\frac{(0)^3}{3} + \frac{5(0)^2}{2} + 2(0) + D 0=D0 = D

    So, the displacement equation is:

    s=−t33+5t22+2ts = -\frac{t^3}{3} + \frac{5t^2}{2} + 2t
  4. Substitute the time for maximum velocity (t=2.5 st=2.5 \, \text{s}) into the displacement equation.

    s=−(2.5)33+5(2.5)22+2(2.5)s = -\frac{(2.5)^3}{3} + \frac{5(2.5)^2}{2} + 2(2.5) s=−15.6253+5(6.25)2+5s = -\frac{15.625}{3} + \frac{5(6.25)}{2} + 5 s=−15.6253+31.252+5s = -\frac{15.625}{3} + \frac{31.25}{2} + 5

    To simplify, use fractions: t=52t = \frac{5}{2}.

    s=−(52)33+5(52)22+2(52)s = -\frac{(\frac{5}{2})^3}{3} + \frac{5(\frac{5}{2})^2}{2} + 2(\frac{5}{2}) s=−12583+5×2542+5s = -\frac{\frac{125}{8}}{3} + \frac{5 \times \frac{25}{4}}{2} + 5 s=−12524+1258+5s = -\frac{125}{24} + \frac{125}{8} + 5

    Find a common denominator, which is 24:

    s=−12524+125×324+5×2424s = -\frac{125}{24} + \frac{125 \times 3}{24} + \frac{5 \times 24}{24} s=−12524+37524+12024s = -\frac{125}{24} + \frac{375}{24} + \frac{120}{24} s=−125+375+12024s = \frac{-125 + 375 + 120}{24} s=250+12024s = \frac{250 + 120}{24} s=37024s = \frac{370}{24} s=18512 ms = \frac{185}{12} \, \text{m} s≈15.4167 ms \approx 15.4167 \, \text{m}

    The distance covered to attain the maximum velocity is 18512 m or 15.42 m (to 2 d.p.)\boxed{\frac{185}{12} \, \text{m} \text{ or } 15.42 \, \text{m (to 2 d.p.)}}.

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