1. A 0.150-kg, 50.0-cm-long uniform bar has a small 0.050-kg mass glued to its l
ID: 1348872 • Letter: 1
Question
1. A 0.150-kg, 50.0-cm-long uniform bar has a small 0.050-kg mass glued to its left end and a small 0.130-kg mass glued to the other end. You want to balance this system horizontally on a fulcrum placed just under its center of gravity.
How far from the left end should the fulcrum be placed?
2. Two people carry a heavy electric motor by placing it on a light board 2.40 m long. One person lifts at one end with a force of 380 N , and the other lifts the opposite end with a force of 620 N .
What is the weight of the motor?
Where along the board is its center of gravity located?
Suppose the board is not light but weighs 210 N , with its center of gravity at its center, and the two people each exert the same forces as before. What is the weight of the motor in this case?
Where is its center of gravity located?
3. To strengthen his arm and chest muscles, an 85.0 kgathlete 2.00 m tall is doing a series of push-ups as shown in the figure below (Figure 1) . His center of mass is 1.20 m from the bottom of his feet, and the centers of his palms are 30.0 cm from the top of his head. Find the force that the floor exerts on each of his feet and on each hand, assuming that both feet exert the same force and both palms do likewise.
Find the force that the floor exerts on each of his feet, assuming that both feet exert the same force.
Find the force that the floor exerts on each of his hand, both palms exert the same force.
4. Two forces equal in magnitude and opposite in direction, acting on an object at two different points, form what is called a couple. Two antiparallel forces with equal magnitudes F1=F2=7.80 N are applied to a rod as shown in the figure
What should the distance l between the forces be if they are to provide a net torque of 6.00 Nm about the left end of the rod?
Is the sense of this torque clockwise or counterclockwise?
Repeat part A for a pivot at the point on the rod where F 2 is applied.
Repeat part B for a pivot at the point on the rod where F 2 is applied.
5. A circular steel wire 1.92 m long must stretch no more than 0.30 cm when a tensile force of 400 N is applied to each end of the wire.
What minimum diameter is required for the wire?
6. A steel cable with cross-sectional area 2.80 cm2 has an elastic limit of e0=2.40×108Pa.
Find the maximum upward acceleration that can be given an elevator of mass 1230 kg supported by the cable if the stress is not to exceed one-third of the elastic limit.
7. A uniform, 6.8-m-long beam weighing 5540 N is hinged to a wall and supported by a thin cable attached 1.2 mfrom the free end of the beam. The cable runs between the beam and the wall and makes a 47 angle with the beam.
What is the tension in the cable when the beam is at an angle of 28 above the horizontal?
Explanation / Answer
1.
Find the center of gravity of the system
x = [m1(L/2) + m2*0 + m3*L] / m1 + m2 + m3
= ( 0.15*(50/2)+ 0.05*0 + 0.130*50 )/ (0.15+0.05+0.130)
= 39.4 cm
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.