Calculating Velocity, Acceleration, and Net Force for a Bungee Jumper

[cary5]

have a question pleasezzzzzzzzz help :)
a man of 80 kg falls for 5s befor the bungee cords start to stresch. it takes 3s to bring the man to rest.
(a) what is the man's velocity before the bungee cord starts to strech
(b) what is his acc. before and after the cord stars to strech
(c) what is the ave. net force on the man

i don't knoe if the man is on Earth so can't calculat for velocity non of the formulas work

 

[berkeman]

have a question pleasezzzzzzzzz help :)
a man of 80 kg falls for 5s befor the bungee cords start to stresch. it takes 3s to bring the man to rest.
(a) what is the man's velocity before the bungee cord starts to strech
(b) what is his acc. before and after the cord stars to strech
(c) what is the ave. net force on the man

i don't knoe if the man is on Earth so can't calculat for velocity non of the formulas work

Of course he's on Earth. Where else in the galaxy to people bungee jump?

So show us the kinematic equations of motion for constant acceleration (the ones you are learning to use for gravity-based questions like this), and show us your work on the solutions to the above questions... You must show your work here before we can offer tutorial help (see the Rules link at the top of the page).

 

[cary5]

Of course he's on Earth. Where else in the galaxy to people bungee jump?

So show us the kinematic equations of motion for constant acceleration (the ones you are learning to use for gravity-based questions like this), and show us your work on the solutions to the above questions... You must show your work here before we can offer tutorial help (see the Rules link at the top of the page).

ok so Vf=Vi+at
=0+(-9.81)(5s)
=-49.1 m/s
acc. before the b cord statrts to strch would be -9.81m/s2

 

[berkeman]

ok so Vf=Vi+at
=0+(-9.81)(5s)
=-49.1 m/s
acc. before the b cord statrts to strch would be -9.81m/s2

Great!

 

[cary5]

Great!

so the acc after the b cord starts to stesh is (Vf-Vi)/t
Vi is the velocity we just calculated and Vf is 0 =(-49.1-0)/3s
-16.4 m/s2

the Vi and Vf of the whole systm is 0. Fnet=pf-pi/t
0-0/3
is the net force 0N?

 

[berkeman]

so the acc after the b cord starts to stesh is (Vf-Vi)/t
Vi is the velocity we just calculated and Vf is 0 =(-49.1-0)/3s
-16.4 m/s2

the Vi and Vf of the whole systm is 0. Fnet=pf-pi/t
0-0/3
is the net force 0N?

They ask for the average net force, which I think is zero as you say. That's because the higher force (acceleration) acts for a proportionally shorter time.

 

[cary5]

They ask for the average net force, which I think is zero as you say. That's because the higher force (acceleration) acts for a proportionally shorter time.

ok thak you