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Physics Help >> Index to Physics Homework Help » Simple Equilibrium
Equilibrium Problems
1. An object acted on by three forces moves with constant velocity. One force acting on the object is in the positive x direction and has a magnitude of 6.5 N; a second force has a magnitude of 4.4 N and points in the negative y direction. Find the magnitude of the third force acting on the object. 2.
3. Arlene is to walk across a "high wire" strung horizontally between two buildings 15.0 m apart. The sag in the rope when she is at the mid-point should not exceed 11°. If her mass is 47.0 kg, what must be the tension in the rope?
4. A child weighing 29 kg is on a swing supported by two chains. Another child is pulling the swing back so that the chains make a 30 degree angle with the vertical. What force is exerted by each chain?
5. A 32.53 N light hangs from two cables at angles 78.3 and 60.2 with respect to the ceiling. what is the tension in the first cable?
6. Two blocks on a ramp are connected by a string and tied to a wall. The mass of the lower block is 1.0 kg; the mass of the upper block is 2.0 kg. Given that the angle of the incline is 31 degrees, find the tensions in (a) the string connecting the two blocks and (b) the string tied to the wall.
7. Mass A (211 grams) was hung at 259º and mass B (355 grams) at 295º on the force table. Adding an unknown mass, C at 0º, the system of masses will be in equilibrium at 147º. The spring scale reading is 849 grams. What is the mass of C?
ANSWERS TO EQUILIBRIUM PROBLEMS
At equilibrium, since acceleration is zero, net force is zero. The resultant of the three forces is zero.
√(4.42 + 6.52) = 7.9
ø = tan-1( 4.4/6.5) = 34º
The third force is 7.9 N 146º from the positive x direction.
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7. At equilibrium, the net force is zero.
Therefore, the sum of the components in the x direction is zero:
a + b + c + d = 0
-211sin11º + 355sin25º - 849sin57º + d = 0
d =602
The unknown mass is 602 grams.
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A 10-kg sign is suspended by three ropes, each supporting an equal portion of the sign's weight. The two end ropes make an angle of 70º to the horizontal. What is the tension on each of the ropes?
