A particle is moving at a constant speed in a counterclockwise circle of radius r about the
point x = y = 0. At a certain instant it is at
x = −r, y = 0.
What is the direction of its acceleration at
that instant?
A. It is along ˆı.
B. It is along −ˆj.
C. It is along ˆj.
D. It is along −ˆı.

Acarpenter builds an exterior house wall with a layer of wood 2.9 cm thick on the outside and a layer of styrofoam insulation 2.3 cm thick on the inside wall surface. the wood has k=0.080w/(m⋅k), and the styrofoam has k= 0.010 w/(m⋅k). the interior surface temperature is 19.0 ∘c , and the exterior surface temperature is -15.0 ∘c . a.)what is the temperature at the plane where the wood meets the styrofoam? celsius b.)what is the rate of heat flow per square meter through this wall? /m^2