1 6 ANSWERS TO PRACTICAL qUESTlONS 



8. If a ball be dropped from a high tower it will strike the 

 earth a little east of a vertical line. IV hy is this ? 



In the daily revolution of the earth on its axis, from west to 

 east, the top of the tower moves faster than the bottom, be- 

 cause it passes through a larger circle. When, therefore, the 

 ball falls, it retains that swifter easterly motion and so strikes 

 east of the vertical. 



9. // is stated that a suit was once brought by the driver of 

 a light-wagon against the owner of a coach for damages caused 

 by a collision. The complaint was that the latter was driving 

 so fast, that when the two carriages struck, the driver of the 

 former was thrown forward over the dash-board. Show how 

 his own testimony proved him to have been at fault. 



When the light-wagon was suddenly stopped, its driver went 

 on by his inertia with the same speed at which the wagon was 

 moving. That this threw him forward over the dash-board, 

 proves his speed to have been unusual. 



10. Suppose a train moving at the rate of '30 miles per hour ; 

 on the rear platform is a cannon aimed parallel with the track 

 and in a direction precisely opposite to the motion of the car. 

 Let a ball be discharged with the exact speed of the train, 

 where would it fall? 



In a vertical line to the track. The two equal, opposite 

 motions would exactly destroy each other. 



11. Suppose a steamer in rapid motion and on its deck a 

 man jumping. Can he jump further by leaping the way the 

 boat is moving or in the opposite direction ? 



It will make no difference as long as he jumps on the deck. 

 Should he jump off the boat, then the effect would be different. 



12. Why is a running jump longer than a standing one? 

 Because the motion gained in running is retained in the 



jump and adds to its distance. 



13. If a stone be dropped from the mast-head of a vesselin 

 motion, will it strike the same spot on the deck that it would if 

 the vessel were at rest ? 



It will. It falls with the motion of the vessel, and goes just 

 as far forward while falling as the vessel does. 



