The diagram shows a weightlifter in the initial stages of his lift. He lifts two 70 kg masses connected to a 10 kg bar. In addition, there are two upward forces : 795N and 810N
a. Calculate the total weight that he is lifting?
b. Calculate the size of the acceleration of the weights during the lift.
To calculate the total weight that the weightlifter is lifting, we need to consider the weight of the masses and the weight of the bar.
a. Calculate the weight of the masses:
The weight of an object is given by the formula: Weight = mass × acceleration due to gravity.
In this case, the mass of each 70 kg mass is 70 kg. The acceleration due to gravity is approximately 9.8 m/s².
Weight of one 70 kg mass = 70 kg × 9.8 m/s² = 686 N
Since there are two 70 kg masses, the total weight of the masses is:
Total weight of masses = 2 × 686 N = 1372 N
b. Calculate the weight of the bar:
The weight of an object is given by the formula: Weight = mass × acceleration due to gravity.
In this case, the mass of the bar is 10 kg. The acceleration due to gravity is approximately 9.8 m/s².
Weight of bar = 10 kg × 9.8 m/s² = 98 N
c. Calculate the total weight that the weightlifter is lifting:
Total weight = Weight of masses + Weight of bar
Total weight = 1372 N + 98 N
Total weight = 1470 N
Therefore, the weightlifter is lifting a total weight of 1470 N.
To calculate the size of the acceleration of the weights during the lift, we need to consider the net force acting on the system.
Net force = Sum of all forces acting on the system
In this case, the two upward forces (795 N and 810 N) are acting against the downward force of gravity. The net force can be calculated as follows:
Net force = (795 N + 810 N) - (Weight of masses + Weight of bar)
Net force = (795 N + 810 N) - (1372 N + 98 N)
Net force = 1605 N - 1470 N
Net force = 135 N
Using Newton's second law of motion, we know that force equals mass times acceleration:
Net force = Mass of system × acceleration
Rearranging the equation, we can solve for the acceleration:
acceleration = Net force ÷ Mass of system
acceleration = 135 N ÷ (2 × 70 kg + 10 kg)
acceleration = 135 N ÷ 150 kg
acceleration ≈ 0.9 m/s²
Therefore, the size of the acceleration of the weights during the lift is approximately 0.9 m/s².