Question

Your car keys have fallen through a sewer grating. You can see them, perched precariously on a ledge. You are able to hook the ring with a bent paper clip attached to your grimy shoelace and pull it upward with constant acceleration. Just before the lace snaps, sending the keys into the depths, you know that the upward velocity was 1.34 m/s and that you had lifted the keys 0.44 m above the ledge. The tension on the shoelace just before it snapped was 10.1 N. What is the mass of the keys?

Answer 1

m=0.853 kg

Step-by-step explanation:

net Force = ma

There are two forces the tension in the shoelace and the weight of the keys

net Force = Tension - Weight = m*a

`T-m*g=m*a`

`T=m*(g+a)`

to find a you know vf= 1.34 m/s, after moving d=0.44m, vi=0 m/s

`Vf^2=Vi^2+2*a*d`

`1.34^2(m/s)=0+2(a)(0.44m)`

`a=2.04(m/s^2)`

`T=m*(g+a)`

`10.1N=m*(9.8+ 2.04)(m/s^2)`

`m=(10.1)/(11.84)`

`m=0.853 kg`