. College algebra, with applications. herefore no unit of force has as yet been definedspecifically. Let us take the pound as unit of mass. Thenthe unit of force will be that force which, acting upon a massof one pound, will produce an acceleration of one foot persecond per second. This unit of force is called a the pound as a unit of mass, and the poundal as aunit of force are very different things. Finally, the weightof a pound is different from either of these. The weight ofa pound according to (3) is equal to of those force unitswhich we have agreed to call poundals. S
. College algebra, with applications. herefore no unit of force has as yet been definedspecifically. Let us take the pound as unit of mass. Thenthe unit of force will be that force which, acting upon a massof one pound, will produce an acceleration of one foot persecond per second. This unit of force is called a the pound as a unit of mass, and the poundal as aunit of force are very different things. Finally, the weightof a pound is different from either of these. The weight ofa pound according to (3) is equal to of those force unitswhich we have agreed to call poundals. Since tliis weightis a force, it may also be used as a unit of force. This unitof force, the weight of a pound, is called a pound of (4) one pound of force = poundals where one poundal is the force which, acting upon a mass of onepound, produces an acceleration of one foot per second persecond. By means of (4) it is easy to convert forces expressed inpounds into poundals and vice versa. 126 QUADRATIC FUNCTIONS [Art. 81. Fig. 39 81. Motion of a projectile under the influence of gravity. In Fig. 39 let the positive ^-axis be directed verticallyupward, and let the a;-axis be a horizontal line in the plane of the curved pathdescribed by a pro-jectile which startsfrom the point Pqwhose coordinatesare (% ?/y). LetV^ and Vy be thecomponents of theinitial velocity Vand let us count time (in seconds) from the moment in whichthe projectile begins its flight. If gravity were not acting,the projectile would after t seconds reach a point whose co-ordinates are (compare equations (5) Art. 79) The action of gravity has no effect upon the first ofthese two equations, which represents the horizontal com-ponent of the motion; but it will cause the projectile tobe in a lower position at every instant than it would oc-cupy if gravity were not acting. This eifect of gravityis taken care of by addition of the term — \ gt^ to theright member of the second equation.* Thus we obtain th
Size: 2194px × 1139px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, bookpublishe, booksubjectalgebra
