Question

A large fish hangs from a spring balance supported from the roof of an elevator. If the elevator has an upward acceleration of 2.45 m/s2 and the balance reads 60.0 N , what is the true weight of the fish?

SET UP
Draw a sketch of the physical situation, and identify the moving object or objects to which you will apply Newton’s 2nd law.
Draw a free-body diagram for each chosen object, showing all the forces acting on that object. Label the magnitudes of unknown forces with algebraic symbols. Usually, one of the forces will be the object’s weight; it is generally best to label this as mg.
Show your coordinate axes explicitly in each free-body diagram, and then determine components of forces with reference to these axes. If you know the direction of the acceleration, it is usually best to take that direction as one of the axes.
SOLVE
Write the equations for Newton’s 2nd law in component form:
∑Fx=max and ∑Fy=may.
If more than one object is involved, repeat step 4 for each object.
REFLECT
Check particular cases or extreme values of quantities, when possible, and compare the results for these particular cases with your intuitive expectations. Ask yourself, "Does this result make sense?" Think about what you have learned from the problem that you can apply to other problems in the future.

For which of the following object(s) will you need to draw a free-body diagram to solve the problem?

For which of the following object(s) will you need to draw a free-body diagram to solve the problem?

the elevator only

the elevator and the spring balance

the spring balance only

the fish only

the fish and the spring balance

the fish, the elevator, and the spring balance

Answer 1

Neuton 2h のN = 60N 81 feD fish nee reeded ラ 48