## Sample Problems

1. What gravitational force exists between two 3 kg balls placed 7.25 m apart?
2. A gravitational force of 1.7 x 10-10 N exists between two objects of equal mass. They are separated by 5 m. What is the mass of each object?
3. A sphere weighing 9800 N and another sphere weighing 1960 N are separated by 4 m. What gravitational force exists between them?
4. An unbalance force gives a 2 kg mass an acceleration of 5 m/s2. What is the magnitude of the force?
5. A 20 N force gives a stone an acceleration of 4 m/s2. What is the weight of the stone?
6. A 5 kg rocket is acted upon by an upward force of 59 N due to the thrust produced by its engines. What is the rockets' weight? Draw the free-body diagram representing these forces. What is the unbalanced force? What acceleration does it cause?
7. A rope attached to an 80 N wagon pulls it to the right with an acceleration of 0.5 m/s2. What is the mass of the wagon? What is the unbalanced force causing this acceleration?
8. A 65 N boy sits on a sled weighing 52 N on a horizontal surface. The coefficient of friction between the sled and the snow is 0.012. What is the magnitude of the frictional force? The sled is pulled at constant speed by a rope held horizontally. What is the tension (the pull) in the rope?
9. A 100 N force is applied to a 10 kg box to push it across a horizontal surface. A frictional force of 20 N exists. What is the acceleration of the box?
10. A 40 N box is pushed across a horizontal surface at constant speed by a 14 N force. What is the frictional force? What is the coefficient of friction?
11. Now a 20 N force is applied in number ten rather than a 14 N force. What is the acceleration of the box?
12. A rocket of mass "m" is accelerated upward by a force giving it an acceleration of 3 g (or three times the acceleration due to gravity). What is the magnitude of this force in terms of "m" and "g?"