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Forces Test Review
1. What is the definition of Fnet? An unbalanced force
2. How do you find Fnet on a flat surface if all four forces are known? Vector addition (subtract opposing forces)
3. How do you find Fnet on an inclined plane? Fnet=Fgsinθ
4. How do you find FN on a flat surface? Same as Fg
5. How do you find FN on an inclined plane? FN=Fgcosθ
6. How do you find Ff when the forces are unbalanced? Use coefficient of friction in the equation Ff=µFN
7. How do you find Ff when the forces are balanced? Same as Fapp
8. How do you find FT when there is more than one tension force (multiple ropes) for a nonmoving object? FT=FN/cosθ
then divide by number of ropes
9. State all three laws of motion
10. What is the cause of something to accelerate? A net force
11. What are three things that an unbalanced force can cause an object to do? to start moving, stop moving or change
direction
12. A truck is being pulled out of the mud with a rope connected to another truck. The weight of the stuck truck is
25,000N and the ground exerts a 19,000N force on the truck. Frictional force is 800N and the tension force from
the towing truck is 6,000N. Draw a free body diagram of the situation.
FN = 19,000N
FT = 6,000N
Ff = 800N
Fg = 25,000N
13. What is the tendency of an object to maintain its current state of motion? inertia
14. A car goes forward along a level road at constant velocity. What must the additional force needed to bring the car
into equilibrium be? (greater than normal force, less than normal force, or zero) zero…it’s already in equilibrium
15. What is true about an object if a net force is acting on it? It’s accelerating, changing direction, unbalanced
16. A book that weighs of 100N is pushed across a level desk surface at an acceleration of 0.5 m/s2. What net force
acts on the book to make it accelerate? 5.1N
17. According to Newton’s second law, when the same force is applied to two objects of different masses, the object
with greater mass will experience a less acceleration and the object with less mass will experience more
acceleration.
18. Two perpendicular forces, one of 40.0 N directed upward and the second of 55.0 N directed to the right, act
simultaneously on an object with a mass of 30.0 kg. What is the magnitude of the resultant acceleration of the
object? 2.27 m/s2
19. An airplane with a mass of 2.4  104 kg tows a glider with a mass of 0.95  104 kg. If the airplane propellers
provide a net forward thrust of 4.6  104 N, what is the acceleration of the glider? 1.37 m/s2
20. A hammer drives a nail into a piece of wood. Identify an action-reaction pair, and compare the forces exerted by
each object. Equal and opposite forces. Hammer is action on nail & nail is reaction on hammer OR nail is action
on wood & wood is reaction on nail.
21. A change in the force of gravity acting on an object will affect the object’s weight.
22. In a game of tug-of-war, a rope is pulled to the left with a force of 85 N and to the right with a force of 119 N.
What is the magnitude and direction of the net external force on the rope? 34N to the right
23. A 30 kg book is pushed along a desk at a constant speed with a horizontal applied force of 65 N.
a. Draw and label a complete free-body diagram identifying all forces acting on the book.
FN
Ff
30kg
Fg
Fapp = 65N
b. What is the force of friction acting on the book as it slides? 65N
c. How much is the normal force? 294N
d. Determine the coefficient of kinetic friction between the book and the desk. 0.22
24. A 15 kg flowerpot is tied with a string that goes around each side of the pot as shown.
a. Label the free body diagram for the flowerpot.
FN
FT1
45°
FT2 FT3
15kg
b. What is the tension in each string? 69.3N
Fg
25. A clean up worker is putting debris in a wheelbarrow when a 3-kg tire comes lose and begins rolling down a steep
hill 35° to the horizontal.
FN
a. Draw the free body diagram.
Ff
3kg
35°
Fg
b. What is the normal force? 24.1N
c. What is the net force? 16.9N
d. What is the acceleration of the wheelbarrow? 5.6 m/s2