In a normal-tangential coordinate system, by convention, the positive normal direction is defined as: a)- towards the center of curvature b)- away from the center of curvature c)- tangent to the motion d)- in the opposite direction to the motion

The temperature of air decreases as it is compressed by an adiabatic compressor. a)- true b)- false

Coiled springs ought to be very strong and stiff. si3n4 is a strong, stiff material. would you select this material for a spring? explain.

Ariver flows from north to south at 8 km/h. a boat is to cross this river from west to east at a speed of 20 km/h (speed of the boat with respect to the earth/ground). at what angle (in degrees) must the boat be pointed upstream such that it will proceed directly across the river (hint: find the speed of the boat with respect to water/river)? a 288 b. 21.8 c. 326 d. 30.2