  The rotation states of kilometer sized near earth asteroids are known to be
affected by the YORP effect. In a related effect, Binary YORP (BYORP) the
orbital properties of a binary asteroid evolves under a radiation effect mostly
acting on a tidally locked secondary. The BYORP effect can alter the orbital
elements in $\sim 10^{4-5}$ years for a $D_{p}=2\;km$ primary with a
$D_{s}=0.4\; km$ secondary at $1\; AU$. It can either separate the binary
components or cause them to collide. In this paper we devise a simple approach
to calculate the YORP effect on asteroids and BYORP effect on binaries
including $J_2$ effects due to primary oblateness and the sun. We apply this to
asteroids with known shapes as well as a set of randomly generated bodies with
various degrees of smoothness. We find a strong correlation between the
strengths of an asteroid's YORP and BYORP effects. Therefore, a statistical
knowledge on one, could be used to estimate the effect of the other. We show
that the action of BYORP preferentially shrinks rather than expands the binary
orbit and that YORP preferentially slows down asteroids. This conclusion holds
for the two extremes of thermal conductivities studied in this work and
assuming the asteroid reaches a stable point, but may break down for moderate
thermal conductivity. The YORP and BYORP effects are shown to be smaller than
what could be naively expected due to near cancellation of the effects on small
scales. Taking this near cancellation into account, a simple order of magnitude
estimate of the YORP and BYORP effects as function of the sizes and smoothness
of the bodies is calculated. Finally, we provide a simple proof showing that
there is no secular effect due to absorption of radiation in BYORP.
