lecturenotes-Feb3

# lecturenotes-Feb3 - Questions A block of mass M is hung by...

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A block of mass M is hung by ropes as shown. The system is in equilibrium. The point O represents the knot, the junction of the three ropes. Which of the following statements is true concerning the magnitudes of the three forces in equilibrium? a) F 1 + F 2 = F 3 b) F 1 = F 2 = 0.5 × F 3 c) F 1 = F 2 = F 3 d) F 1 > F 3 e) F 2 < F 3 Questions
A block of mass M is hung by ropes as shown. The system is in equilibrium. The point O represents the knot, the junction of the three ropes. Which of the following statements is true concerning the magnitudes of the three forces in equilibrium? Questions Equilibrium means F  = 0 F 1 cos θ− F 2 cos θ = 0 F 1 = F 2 2 F 1 sin = F 3 F 1 = F 3 when =30 o F 1 + F 2 = F 3 when =90 o F 1 > F 3 when < 30 o F 2 < F 3 when > 30 o

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Consider the situation shown in the drawing. Block A has a mass 1.0 kg and block B has a mass 3.0 kg. The two blocks are connected by a very light rope of negligible mass that passes over a pulley as shown. The coefFcient of kinetic friction for the blocks on the ramp is 0.33. The ramp is angled at θ = 45 ° . At time t = 0 s, block A is released with an initial speed of 6.0 m/s. What is the tension in the rope? a) 11.8 N b) 7.88 N c) 15.8 N d) 13.6 N e) 9.80 N ±ree-Body Diagrams: Normal ±orce
Consider the situation shown in the drawing. Block A has a mass 1.0 kg and block B has a mass 3.0 kg. The two blocks are connected by a very light rope of negligible mass that passes over a pulley as shown. The coefFcient of kinetic friction for the blocks on the ramp is 0.33. The ramp is angled at θ = 45 ° . At time t = 0 s, block A is released with an initial speed of 6.0 m/s. What is the tension in the rope? ±ree-Body Diagrams: Normal ±orce mg T f k ± N T f k = T μ k mg = ma a = T m 0.33 g 3 mg sin 45 o T f k = 3 ma 3 mg sin 45 o T k 3 mg cos 45 o = 3 ma sin 45 o T 3 mg 0.33cos 45 o = a g T 3 mg = a g 0.473 ± N mg f k T 3 m = T m 0.33 g 0.473 g T = 3 2 0.803 ( ) g = 11.8 N

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Chapter 7 - Kinetic energy and Work Each energy is associated with a “scalar” which defnes a state oF a system at a given time. Different energies: • Kinetic/translation • Gravitational potential • Heat energy • Electromagnetic energy • Strain or elastic energy Kinetic Energy is associated with the state of motion KE = 1 2 mv 2 Units oF Joules: 1 J = kg·m 2 /s 2 • KE depends on speed not • KE doesn’t depend on which way something is moving or even if it’s changing direction • KE is ALWAYS a positive scalar v ( here v 2 = v v = v 2 )
Magnitude of “Kinetic Energy” Kinetic Energy is associated with the state of motion • KE depends on speed not • KE doesn’t depend on which way something is moving or even if it’s changing direction v ( here v 2 = v 2 ) 1) Electron ( e -) moving in Copper m e = 9.11 × 10 -31 kg and v ~ 1 × 10 6 m/s KE = 7 × 10 -19 J ( ~ 4 eV ) 2) Bullet traveling at 950 m/s (3100 ft/s) .

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lecturenotes-Feb3 - Questions A block of mass M is hung by...

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