1. Chapter 4 Additional Problems

2. 1. A sphere with a weight of 10 N hangs from a rope
1. A sphere with a weight of 10 N hangs from a rope. If you push on the side of the sphere such that the rope is pushed to an angle of 25º to vertical, what horizontal force must you apply?

3. The force you apply is the opposite of the angle
The force you apply is the opposite of the angle. The weight becomes the adjacent. Tan 25º = F/10N F = 4.7 N

4. 2. A rope is used to pull a box across a level floor
2. A rope is used to pull a box across a level floor. The force applied to the rope is 560 N and the rope is at an angle of 40º to the ground. What is the frictional force between the ground and the box?

5. The frictional force is balanced by the horizontal component of the force on the rope. cos 40º = Ff / 560 Ff = 429 N

6. 3. A sled is moving across an ice rink at a velocity of 15 m/s
3. A sled is moving across an ice rink at a velocity of 15 m/s. If the sled stops after moving 20 meters, what is the coefficient of friction between the sled and the ice?

7. v2 = v02 + 2ax 02 = 152 + 2a20 a = 5. 6 m/s2 F = ma Ff = m x 5
v2 = v02 + 2ax 02 = a20 a = 5.6 m/s2 F = ma Ff = m x 5.6 FN = wt = mg = m x 10 m = Ff / FN m = (m x 5.6)/ (m x 10) m = 0.560

8. 4. A mover pulls a dolly (hand truck) at an angle of 60º to the horizontal. If the horizontal component of the force is 47 N, what force does the mover apply to the handle?

9. We know the horizontal force, which is the adjacent of the triangle, we want to find the hypotenuse. cos 60º = 47/ F F = 47/ cos 60º F = 94 N

10. 5. A rock with a weight of 2000 N is accelerated horizontally at 3 m/s
5. A rock with a weight of 2000 N is accelerated horizontally at 3 m/s. What is the net force on the rock?

11. Wt = mg 2000 N = m x 10 m = 200 kg F = ma F = 200 x 3 F = 600 N