quick simple physics problem help!

mAKiTO

Colombia4171 Posts

September 23 2008 03:00 GMT

ok i ahd a set of problems on a basic physics class and im stock in one help

problem reads:

A crane lifts a 2000-kg mass upwards. if the tension in the cable is 20,000 N, what is the acceleration of the block?

what I did is use
a= f/m = 20000N/2000 kg = 10m/s square

but the answer says its 0.2m/secs square

I know that if I divided 2000N by 500 and get 400 and then 400N / 2000kg gives me 0.2m/sec square but i dont get why at all lol can someone plz explain this to me

randombum

United States2378 Posts

September 23 2008 03:02 GMT

Hi. My name is gravity, if you live on earth I pull you down with nearly constant acceleration of 9.8 m/s^2. In other words I exert 9.8 Newtons of force of on you for every kilogram you weigh.

mAKiTO

Colombia4171 Posts

September 23 2008 03:15 GMT

if i multiply the 2000kg by g it gives me 19600

but then what do I do with that number? if I divide by 20000 i still dont get the answer...

im really bad at this lol so dont laugh at me ._.

IntoTheWow

is awesome32278 Posts

September 23 2008 03:18 GMT

Chromyne

Canada561 Posts

September 23 2008 03:20 GMT

Free body diagrams! They help a lot

Fnet = T + Fg, where T = tension force and Fg is the force of gravity.

Fnet = 20 000N + (-9.81m/s^2)(2000kg)
Fnet = 380 N

Find the acceleration of the block:

F = ma
380 N = (2000kg)(a)
a = 0.19 m/s^2

which is roughly 0.2 m/s^2.

mAKiTO

Colombia4171 Posts

September 23 2008 03:21 GMT

thank you Agu.. now that I see it like that I get it =D

mAKiTO

Colombia4171 Posts

September 23 2008 03:21 GMT

thanks guys <3 i been in college for 2 years and its the first physics class I ever take in my life lol

IntoTheWow

is awesome32278 Posts

September 23 2008 03:28 GMT

No problem.

Chill

Calgary25996 Posts

September 23 2008 03:53 GMT

On September 23 2008 12:02 randombum wrote:
Hi. My name is gravity, if you live on earth I pull you down with nearly constant acceleration of 9.8 m/s^2. In other words I exert 9.8 Newtons of force of on you for every kilogram you weigh.

loool

Meta

United States6225 Posts

September 23 2008 03:57 GMT

#10

I wish I could have said this- thanks for making it funny =)

randombum

United States2378 Posts

September 23 2008 04:06 GMT

#11

On September 23 2008 12:57 Meta wrote:

Show nested quote +

I wish I could have said this- thanks for making it funny =)

I'm glad it was funny, but it would've been far better if he managed to get the answer from it. O well, he got the answer soon enough after anyways.

Grobyc

Canada18410 Posts

September 23 2008 04:18 GMT

#12

On September 23 2008 12:15 mAKiTO wrote:
if i multiply the 2000kg by g it gives me 19600

but then what do I do with that number? if I divide by 20000 i still dont get the answer...

im really bad at this lol so dont laugh at me ._.

haw haw to you