Bob bench presses a 50 lb barbell. He maintains a constant speed on the way up and on the way down. If the barbell moves 75 cm in each direction how much work does Bob do on the barbell on the way up and the way down? What is the total work done?
Cool
To determine the work done by Bob on the barbell, we can use the formula:
Work = Force x Distance
First, let's calculate the work done by Bob on the barbell on the way up.
The force in this case is equivalent to the weight of the barbell, which is 50 lbs. We need to convert this weight to Newtons since the unit of work in SI units is Joules.
1 lb ≈ 4.448 N (approximately)
So, the weight of the barbell is 50 x 4.448 ≈ 222.4 N.
The distance traveled by the barbell on the way up is given as 75 cm, which we need to convert to meters:
75 cm = 75/100 = 0.75 m
Now, we can calculate the work:
Work = Force x Distance
Work = 222.4 N x 0.75 m
Work = 166.8 J
Therefore, Bob does approximately 166.8 Joules of work on the barbell on the way up.
Similarly, on the way down, the work done will be the same since Bob maintains a constant speed, regardless of the direction.
Total work done = Work on the way up + Work on the way down
Total work done = 166.8 J + 166.8 J
Total work done = 333.6 J
Thus, the total work done by Bob on the barbell is approximately 333.6 Joules.