Date elevatorlkngs from a spring scale calibrated in newtons

Date: elevatorlkngs from a spring scale calibrated in newtons that is atached to the (to pts to the ceiling of an (e) Draw a free body diagrams for the elevator and the block (b) find the scale reading when the elevator is ascending with a constant speed of 30 mi\' (c) find the scale reading when the elevator is descending with a constant speed of 30 ms (d) find the scale reading when the elevator is ascending at 20 m/\'s and gaining speed at a rate of 3.0 m/s? (e) Suppose that from-0 to-5.0s steadily reduced to zero during the neut 4 0 s, so (e) Suppose that from- 0to-5.0 s, the elevator ascends at a constant speed of 10 m\'s. Its speed is then ly reduced to zero during the next 4.0 s, so that it is at restat-9.0s. Describe the reading of the scale during the 9.0 s. interval 0

Solution

Newton\'s second law: Total Force = Mass*Acceleration => Spring Force - gravitational force = m*a
As you see speed doesn\'t matter. I use up direction as plus.
a)
a=0 => Spring force = m*g = 2.00*10 = 20 N
b)
a=0 => Spring force = m*g = 2.00*10 = 20 N
c)
a=+3 => Spring force = m*a + m*g = 2*3 + 2*10 = 26 N
d)
T0 5 : a=0 => Spring force = m*g = 2.00*10 = 20 N
the elevator slows down in the positive y direction, so the acceleration is negative.

T5 9 : a= (0-10)/4 = -2.5 => Spring force = m*g + m*a = 2*10 + 2*-2.5= 15 N