Rational functions

9000009910

Level: 
A
A body is deformed continuously in a machine press. The density \(\rho \) is inversely proportional to the volume \(V \) of the body, i.e. there exists a constant \(k\) such that \[ \rho = \frac{k} {V }. \] Find the constant \(k\) (including the correct unit) if it is known that the density was \(\rho = 25\: \frac{\mathrm{kg}} {\mathrm{m}^{3}} \) when the body had volume \(V = 2\, \mathrm{dm}^{3}\).
\(50\, \mathrm{g}\)
\(12.5\, \mathrm{g}\)
\(12.5\, \mathrm{m}\)
\(50\, \mathrm{m}\)

9100009902

Level: 
A
The Newton's second law of motion \[ F = m\cdot a \] states that the the acceleration \(a\) of the body is directly proportional to the acting force, \(F\). The positive constant of this proportionality is the mass of the body, \(m\). This law can be also rewritten in the form of inverse proportionality between convenient other quantities. Which of the graphs describes the Newton's second law properly, assuming one of the quantities which appear in the Newton's law is constant?

9100009903

Level: 
A
The resistance \(R\) of a wire is a function of a material constant \(\rho \), the length \(l\) and the cross section \(S\). It can be computed from the formula \[ R =\rho \cdot \frac{l} {S}. \] Assuming two of the quantities are inversely proportional when the other two quantities are constant, identify the graph which describes this relationship properly.

1003118301

Level: 
B
Find the true statement about the function \( f(x)=-1+\frac3{2x-6} \).
The function \( f \) is decreasing on the interval \( (3;\infty) \).
The function \( f \) is decreasing on the interval \( (-3;\infty) \).
The function \( f \) is decreasing on the interval \( (-\infty;6) \).
The function \( f \) is decreasing on the interval \( (-1;\infty) \).