Question

Are the objects described here in static equilibrium, dynamic equilibrium, or not equilibrium at all? Explain.

a. a 200 pound barbell is held above your head
b. a girder is being lifted at a constant speed by a crane
c. a girder is being lowered into place. its is slowing down
d. a jet plane has reached its cruising speed an altitude
e. a box in the back of a truck doesn't slide as the truck stops

Answer 1

Please help!

Answer 2

Static equilibrium means the objoct is not moving.

Answer 3

Kinetic equilibrium means moving at a constant velocity (not accelerating).

Answer 4

Not in equilibrium means accelerating.

Answer 5

Any ideas for a?

Answer 6

Static Equilibrium?

Answer 7

Yup :) Great, how about the next one?

Answer 8

Why is it static though?

Answer 9

My professor wants us to show him why we are choosing this answer... but I am unsure of how to do so.

Answer 10

Because it is not moving it is static and because it is not accelerating, all of the forces acting upon it are balanced so it is in equilibrium.

Answer 11

ok thank you and for the rest of them I got

b. kinetic
c. not in equilibrium
d. not in
e. static

Answer 12

Great job! The only one I get a different answer on is d.

Answer 13

Cruising speed on a plane would be constant speed.

Answer 14

would d be kinetic? I wrote that down at first but then i was thinking and thought it would have to accelerate to get to cruising speed.

Answer 15

am i over thinking it?

Answer 16

It would accelerate to get to cruising speed, but the question is asking about once it reaches cruising speed.

Answer 17

ok ok thank you very much!!

Answer 18

No worries. :)

Answer 19

i have another thread opened up with another question...if you could help if not that's ok!