  We provide scaling relations for the Nusselt number $Nu$ and the friction
coefficient $C_{S}$ in sheared Rayleigh-B\'enard convection, i.e., in
Rayleigh-B\'enard flow with Couette or Poiseuille type shear forcing, by
extending the Grossmann & Lohse (2000,2001,2002,2004) theory to sheared thermal
convection. The control parameters for these systems are the Rayleigh number
$Ra$, the Prandtl number $Pr$, and the Reynolds number $Re_S$ that
characterises the strength of the imposed shear. By direct numerical
simulations and theoretical considerations, we show that in turbulent
Rayleigh-B\'enard convection, the friction coefficients associated with the
applied shear and the shear generated by the large-scale convection rolls are
both well described by Prandtl's (1932) logarithmic friction law, suggesting
some kind of universality between purely shear driven flows and thermal
convection. These scaling relations hold well for $10^6 \leq Ra \leq 10^8$,
$0.5 \leq Pr \leq 5.0$, and $0 \leq Re_S \leq 10^4$.
