Spider-Man holds the bottom of an elevator with one hand. With his other hand, h
ID: 1539924 • Letter: S
Question
Spider-Man holds the bottom of an elevator with one hand. With his other hand, he holds a spider cord attached to a 54-kg box of explosives at the bottom of the cord.
Determine the force that the cord exerts on the box if the elevator is at rest.
Express your answer to two significant figures and include the appropriate units.
Determine the force that the cord exerts on the box if the elevator accelerates up at 1.4 m/s2 .
Express your answer to two significant figures and include the appropriate units.
Determine the force that the cord exerts on the box if the upward-moving elevator's speed decreases at a rate of 1.4 m/s2 .
Express your answer to two significant figures and include the appropriate units.
Determine the force that the cord exerts on the box if the elevator falls freely.
Express your answer to two significant figures and include the appropriate units.
Explanation / Answer
m= mass = 54 kg
a ) force that the cord exerts on the box if the elevator is at rest.
since elevator is at rest.So net force = zero.
force that the cord exerts on the box = Tension = weight of box = mg = 54*9.8 = 529.2 N = 53*101 N
B) force that the cord exerts on the box if the elevator accelerates up at 1.4 m/s2
a= acceleration = 1.4 m/s2
Force exert by cord = Tension (T) = ?
since acceleration is in upward , ma = T - mg
T = m( a+g) = 54*( 1.4 + 9.8) = 604.8 N = 60.48*101 N = 60*101 N
c) the force that the cord exerts on the box if the upward-moving elevator's speed decreases at a rate of 1.4 m/s2 .
T = m( a+g)
since a= - 1.4 m/s2
T = 54*( - 1.4 + 9.8) = 453.6 N = 45.36*101 N = 45*101 N
D) the force that the cord exerts on the box if the elevator falls freely.
in free fall ,net force : ma = mg - T
T = m( g- a)
in free fal a= g
T = m( g- g) = 0 N
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