Newton's Laws - Mission NL9 Detailed Help

A 500-kg upward-moving freight elevator nears its destination and accelerates downward at a rate of 1.6 m/s/s. Fill in all blanks in the diagram below and determine the tension force. (Use the approximation that g ~ 10 N/kg.) ... 
 
(Note: Numbers are randomized numbers and likely different from the numbers listed here.)



 
The big idea in this problem is to use the acceleration of the object to determine the net force; and then to use the net force to determine the value of an individual force - Ftens. The following method will assist your solution to the problem.
  • The mass and acceleration of the object are explicitly stated. The net force can be determined using Newton's second law equation: Fnet = m • a.
  • Neither of the individual forces are explicitly stated. The force of gravity can be determined from the object's mass (see Formula Fix section; use g = 10 N/kg).
  • The net force is the vector sum of all the forces. It has a value (which is the m•a product) and a direction (which is the same direction as the acceleration). In this problem, the direction of the net force is downward. The net force tells who wins the tug-of-war between individual forces (that's the direction) and the winning margin in the war (that's the value). So if the net force is 200 N, down then the downward force wins the tug of war over the upward force; and the winning margin is 200 N. That is, the downward force is bigger than the upward force by 200 N. Once you have determined the net force by multiplying m•a, determine the tension force by using this principle. Take your time and think about it!


 
The mass of an object is mathematically related to its weight by the equation: 
 
Weight = Fgrav = mass • g

where g is the gravitational field strength. The value of g on Earth is 9.8 N/kg (approximately 10 N/kg).

 

The relationship between net force (Fnet), mass (m) and acceleration (a) is expressed by the equation:
 
a = Fnet / m