# Mass, force, speed?

1. Jan 3, 2005

### rcgerrity

i have this question

a crane is raising a steel beam (350 kg) the max tension the supporting cable can take without breaking is 7000 Newtons

a) is it safe to life the beam at a constant speed of 3m/s? prove answer

(the only idea i have is the use of f=ma, but then i am stuck w/acceleration when i need to use speed i just don't know what to do.)

Last edited: Jan 3, 2005
2. Jan 3, 2005

### Parth Dave

if something is travelling at a constant speed, what is its acceleration? What does this mean about your NET force?

3. Jan 3, 2005

### deanchhsw

As a physics student, I cannot be completely sure of answering this as some of experts in this forum would, but I'll do it anyway..

Don't be too mindful of the "3m/s" as a quantity.
however, be mindful that it's moving at a constant speed.
That means there is NO acceleration.

As Dave said, what does that make your Net force?

Draw a free body diagram to see what forces are acting on the steel beam.
Then see if the tension on the cable is greater than 7,000 Newtons.