Question

Spider-Man holds the bottom of an elevator with one hand. with his other hand, he holds a spider cord attached to a 30-kg box of explosives at the bottom of the cord.

part A
Determine the force that the cord exerts on the box if the elevator is at rest.

partB
Determine the force that the cord exerts on the box if the elevator accelerates up at 2.4 m/s^2

part C
Determine the force that the cord exerts on the box if the upward-moving elevator's speed decreases at a rate of 2.4 m/s^2

Part D
Determine the force that the cord exerts on the box if the elevator falls freely.

Answer 1

A. F = mg = 30 x 9.8 = 294 N

B. Applying Fnet = m a

F - mg = ma

F = 30 ( 9.8 + 2.4) = 366 N

C. mg - F = ma

F = m ( g- a) =30 (9.8 - 2.4)

F = 222 N

D. now a= g

so F = m (g -g ) = 0