Use the fact that the speed of light in a vac-uum is about 3.00 � 108 m/s to determinehow many kilometers a pulse from a laserbeam travels in exactly sixhours.

Under the action of a constant force an object accelerates at 7.8 m/s2. what will the acceleration be if (a) the force is halved? (b) the object's mass is halved? (c) the force and the object's mass are both halved? (d) the force is halved and the object's mass is doubled?