No Dokumen SB/MS/T1/DMCS1313/1

No Isu./Tarikh 1/28-12-2005

STATICS EQUILIBRIUM OF FORCE AT A POINT

No Semakan/Tarikh 0

Jum Mukasurat 2

KOLEJ UNIVERSITI TEKNIKAL KEBANGSAAN MALAYSIA

OBJECTIVES To show that the force acting at a point is in equilibrium. THEORY The particle is said to be at equilibrium if it satisfied Newton’s first law of motion, which requires the resultant force acting on a particle to be equal to zero. This condition may be stated mathematically as Σ F = 0 where Σ F is the vector sum of all the forces acting on the particle. For example, Figure 1 shows two forces F1 and F2 acting on a particle. To satisfied the equilibrium, the resolution of these forces in x and y direction should be equal to zero as expressed by the mathematical equation 1 and 2.

→ + Σ Fx = 0, F1 cos θ – F2 cos β = 0 (1) ↑+ Σ Fy = 0, F1 sin θ – F2 sin β = 0 (2)

x

y

Figure 1 Forces at a point

EQUIPMENT 1. Force board 2. Several pulleys 3. A set of weights PROCEDURES 1. Tie three cords to the steel ring. The number of strings equals the number of force

acting at a point. 2. Fixed the pulleys to the sides of the frame. 3. Fixed the spring balance anywhere along the top of the frame. Tie one of the cord to

the spring balance 4. Pass the remaining cords over the pulleys (one cord per pulley). 5. Hang the load hanger at the free end of the cords 6. If necessary adjust the position of the pulley such that the pin on the force board is

located at the centre of the steel ring. 7. Place loads on the load hangers. This will cause the steel ring to move.

F1

F2

θ

β

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SB/MS/T1/DMCS1313/1

8. Adjust the magnitude of the loads on the load hangers to allow the steel ring to return to its original position.

9. Record the magnitude of the load on each of the load hanger and the angle of inclination of each cord

X

YChoose two points on the bar or the string. Measure the horizontal and the vertical between these two points

Figure 2 Diagram how to measure horizontal and vertical distance between two points

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