v MATTER IN RELATION TO MOTION 73 



66. Two forces P and Q act upon a body. If P acted aione it 

 would, in two seconds, produce in the body a velocity of 10 feet per 

 second, while if Q acted alone it would, in three seconds, produce in 

 the body a velocity of 18 feet per second. What velocities will P 

 and Q produce in one second when acting together if the directions 

 in which they tend to move the body are (a) identical ; (b) directly 

 opposed ? 



Note. For the sake of practice the student should work some of 

 these examples, substituting centimetre-gram-second units for those 

 given. 



