# Homework Help: Can we define force if

1. Feb 13, 2012

### -Physician

Can we define force if ......

1. The problem statement, all variables and given/known data
Can we define force if a body from high of $h_1=4m$ goes down to $h_2=−3m$, for time $t=4s$, and with velocity of $v=10\frac{m}{s}$. The acceleration would be $a=\frac{v}{t}=\frac{10\frac{m}{s}}{4s}=2.5 \frac{m}{s^2}.$ Can we define the force using these things? If yes, let me know the formula, if no, let me know :)

2. Relevant equations
none

3. The attempt at a solution
none.

Last edited: Feb 13, 2012
2. Feb 13, 2012

### wukunlin

Re: Can we define force if ......

F = ma, you need the mass as well as acceleration to find the force

3. Feb 13, 2012

### -Physician

Re: Can we define force if ......

I know $F=ma$, but, I have the acceleration, but I don't want mass, I want to know if there's a way to find the Force with distance between two highs , with a velocity for a set time.

4. Feb 13, 2012

### Staff: Mentor

Re: Can we define force if ......

This kinematic data doesn't seem consistent. Did you just make it up?
No.

5. Feb 13, 2012

### -Physician

Re: Can we define force if ......

Yeah, I made it my self, And I see you can't because $m ,m , s, \frac{m}{s}$ wouldn't be able to make $N$ (Newton) or $kg\frac{m}{s^2}$ which is $kg\frac{m}{s^2}=N$

6. Feb 14, 2012

### sankalpmittal

Re: Can we define force if ......

Way too many errors in it.
Firstly you say that object goes from
h1=4m goes down to h2=−3m ?

How can you say that distance will be -3m ???? Distance is scalar !
Secondly , yes we can define displacement to be negative with reference to direction but here body is falling uni-directionally. You have to say that body is falling from distance of 4m to 3m.

Again another error : If body is falling downwards then acceleration will be 9.8 or 10m/s2 i.e constant value. This further implies that the velocity of body will keep on increasing by 9.8 or 10m/s , every second. You just can't say that velocity of body will be uniform here in this case.

Again acceleration is rate of change in velocity , not velocity by time.
And lastly , out of curiosity : Are you assuming another planet where acceleration is 2.5m/s2 ?

You CANNOT define FORCE without using or taking MASS of object in ACCOUNT.

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