Lab 5: Weightlifting

Procedure and Analysis: The lab began with the group making a rough estimate of the force required from ea ch arm to lift the weight up to be about 700N per arm. We then drew a force diagram for the force acting on the barbell and when the lifter held the barbell over his head. Were: the angle=35 degrees Fn= The normal force m= mass g=gravity the force exerted by each arm We then used the following equation W = mg to calculate the weight of the barbell. W= weight m=mass W = 135kg • 9. 1 = 1324. 35 N We then estimate the angle of each arm acting on the bar to be about 60 degrees. We then broke down both Vector F into its component vectors. Since the the group assumed th at the force needed to lift the barbell is the same in each arm we multiply our compone nt vector sin(b) times 2. F = 2W (stn(B)) the force in both arms the angles that Vector F makes with the xaxis F = = 1517. 68 N This calculation is for both arms the force exerted by each arm is about 758. N part S: The group now proceed to make a force diagram for when the barbell was held at wa st level Just before the lift. The group came up with the following diagram. the force in one arm g= gravity Fn= The Normal Force an angle We then procedure to repeat the procedure in part A but realize that their was no ne ed since the Force diagram generated in part B was the exact same diagram as the one i n part A the only difference was that in part B everything was below the xaxis but the calculations would still be the same.

We then proceed to make a force diagram for when the barbell as it is lifted past the eyes. In this diagram the barbell is lifted past the eyes thus the arms are at a 90 degree an When we break the Force vectors into y and x components the x components equal O since there is no force in the x direction thus weight of the barbell an angle. Observations: 1 . There was a 8% variation in in the answers shared in step with the value calculate d in steps 4 9. The group was mostly relying on the weight of the barbell and how much force each arm exerted. 2.

We estimate the angle by assuming that if the arms were too far from each other t en it would be very hard thus a very large angle was out of the picture. Furthermore to lift the barbell with your arms very close together would be Just as hard thus our estimate co uld not be too small either. 3. We did not need to solve both equations in step 9 since both equation are mirror i mages of each other. 4. In steps 12 and 9 the group was essentially solving the same problem the only diffe rence was that in steps 9 the force exerted by the arm were above the x axis and in step 12 they were below the x