Question

While moving out of her dorm room, Bridget carries a 15 kg box to her car, holding it with both arms.
a) How much force must be exerted by each of her arms to support the box?
b) When she gets our her car keys to unlock the door she must shift the box to just one arm. How much force must that arm exert to hold the box?

Answer 1

She has to overcome the force of gravity. To calculate it, F=ma

Answer 2

So, F=(15)(-9.81)

Answer 3

F=-147.15 N

Answer 4

ignoring gravity

Answer 5

oh :/

Answer 6

wait I lied never mind forget I said that

Answer 7

Is the box floating?

Answer 8

Oh, so the force of gravity is -147.15 N

Answer 9

So in order to overcome that, she has to exert an equal force in the opposite direction, so it would be 147.15 N. For each of her arms, you would divide by 2 to get 73.575 N for each arm.

Answer 10

Obviously, for b, the arm has to carry the entire thing, so the arm would have to exert 147.15 N. (If she was using only one arm, as opposed to 2.)

Answer 11

ok my teacher said to use w=mg so do you know how to do it that way?

Answer 12

weight = mass times acceleration of gravity

Answer 13

Oops my bad, it would be the exact same thing. Replace F with W, and a with g

Answer 14

Acceleration of gravity=-9.81 \[m/s ^{2}\], and mass is 15 kg.

Answer 15

ok thanks so much!

Answer 16

No problem!