v MATTER IN RELATION TO MOTION 69 



5. What is meant by Force ? What are the results of the action 

 of force upon a mass ? 



6. Define the Unit of Force. When are two forces said to be 

 equal ? 



7. How is the number of units of force in any force estimated ? 



8. A force F acting on a mass of 5 Ibs. increases its velocity in 

 every second by 12 feet a second ; a second force Fj acting on a 

 mass of 28 Ibs. increases its velocity in every second by 7^ feet a 

 second. Find the ratio of F to F lt 



9. Enunciate Newton's First Law of Motion. Explain what you 

 understand by a natural law. 



10. Explain what is meant by the inertia of a material body, 

 (live as many of the results of the possession of this property by a 

 material body as you can. 



11. How is the weight of a given body estimated? Why is 

 the weight of a body different at the equator and at the poles ? 



12. How would you proceed to determine the value of the 

 acceleration due to gravity ? 



13. Two stones are allowed to drop from the same height but 

 the second stone 5 seconds after the first. How far apart will 

 they be at the end of 2 seconds from the fall of the second stone ? 



14. Find the velocity of a ball thrown into the air 2 seconds after 

 it has passed its highest point. 



15. A body falls from a certain height and on reaching the ground 

 has a velocity of 120 feet per second. Wliat is the height ? 



16. What is the depth of a well if it takes 3 seconds for a stone to 

 fall from the top to the bottom. 



17. A body falls freely from rest. What is its velocity at the end 

 of 1 , 2, 3 seconds respectively ? 



18. A body falls from a tower 144 feet high. Find how long 

 it takes to reach the ground and its velocity just before reaching 

 it? 



19. State the proposition known as the Parallelogram of Forces 

 and give an experimental proof of it. 



20. What is meant by the resultant of two forces acting at a point ; 

 and how can it be determined ? 



21. The horizontal and vertical components of a certain force are 

 equal to the weights of 60 Ibs. and 144 Ibs. respectively. What is 

 the magnitude of the force ? 



22. Forces of 5 and 12 units respectively act at a point. What are 

 their directions when their resultant is greatest and when it is 

 least ? 



Find the resultant when greatest, when least, and when the forces 

 act at right angles to each other. 



23. Draw two lines Ox, Oy at right angles to each other ; two forces 

 act at ; one of 7 units from x to O and one of 1 units from to y ; 

 draw to any scale straight lines to represent these forces ; draw, to 

 the same scale, the straight line (OR) that represents their resultant ; 

 and find from the diagram the number of units of force in the 

 resultant, and the number of degrees in the angle xOR. 



24. Resolve a force of 56 Ibs. into two others, so that the smaller 





