OCR MEI M3 2007 June — Question 1

Exam BoardOCR MEI
ModuleM3 (Mechanics 3)
Year2007
SessionJune
TopicDimensional Analysis

1
    1. Write down the dimensions of the following quantities. \begin{displayquote} Velocity
      Acceleration
      Force
      Density (which is mass per unit volume)
      Pressure (which is force per unit area) \end{displayquote} For a fluid with constant density \(\rho\), the velocity \(v\), pressure \(P\) and height \(h\) at points on a streamline are related by Bernoulli's equation $$P + \frac { 1 } { 2 } \rho v ^ { 2 } + \rho g h = \mathrm { constant } ,$$ where \(g\) is the acceleration due to gravity.
    2. Show that the left-hand side of Bernoulli's equation is dimensionally consistent.
  1. In a wave tank, a float is performing simple harmonic motion with period 3.49 s in a vertical line. The height of the float above the bottom of the tank is \(h \mathrm {~m}\) at a time \(t \mathrm {~s}\). When \(t = 0\), the height has its maximum value. The value of \(h\) varies between 1.6 and 2.2.
    1. Sketch a graph showing how \(h\) varies with \(t\).
    2. Express \(h\) in terms of \(t\).
    3. Find the magnitude and direction of the acceleration of the float when \(h = 1.7\).