(a) An 11.0 kg Salami is supported by a cord that runs to a spring scale, which is supported by a cord hung from the ceiling (Figure-a). What is the reading on the scale, which is marked in weight units? (b) In Figure-b the salami is supported by a cord that runs around a pulley and to a scale. The opposite end of the scale is attached by a cord to a wall. What is the reading on the scale? (c) In Figure-c the wall has been replaced with second 11.0 kg salami, and the assembly is stationary. What is the reading on the scale?
Mass of salami, m = 11 kg.
The free body diagram helps us to understand the different forces acting on the body along with their direction. It is very useful to resolve the forces and find the net force acting on the body.
By drawing the free body diagram for each situation, we can find the reading on the spring scale. All forces acting on the body are to be balanced for the body to be at equilibrium. So, the total force in a given direction is zero.
Force acting on a body according to Newton’s second law, F = ma (i)
Here, F is the force, m is the mass and a is the acceleration of the body.
Free body diagram on salami in the situation (a):
As there is no acceleration for the section (a), using equation (i), we get the net force to be:
Hence, the reading for situation (a) is 108 N
Free body diagram of the spring scale
Free body diagram of salami on salami in the situation (b):
From F.B.D. of Spring Scale, we get the net force is zero for equilibrium. Hence,
From F.B.D. of Salami, the net force at equilibrium is zero. Hence,
As we know from equation (a), we get the reading value as:
Hence, the value of reading is 108 N
From F.B.D. of spring scale
Free body diagram of salami in the situation (c)
For both the salamis, the free body diagram will be the same.
As the same force is acting on both sides, we consider only the left side for calculation
From F.B.D. of Salami, we get the net forces on it is zero. Hence,
As we know from equation (b), we get the reading as:
Hence, the reading value is 108 N.
Figure 5-39 shows an overhead view of a lemon half and two of the three horizontal forces that act on it as it is on a frictionless table. Force has a magnitude of 6.00 N and is at . Force has a magnitude of 7.00 N and is at . In unit-vector notation, (a) what is the third force if the lemon half is stationary, (b) what is the third force if the lemon half has the constant velocity v and(c) what is the third force if the lemon half has the varying velocity where t is time?
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