Velocity from using only distance and mass?

Question

Hey, i was wondering whether or not it was possible to find the velocity on an object if you only know the distance the object travelled, and its mass.

If you know an equation that may help me please post.

Incase your wondering i need to find the velocity of an object weighing 80 grams, and falling a distance of 5 cm.

Thanks for your help.

Answer 1

It is not possible, unless we know the initial velocity (or time). If we know it started from rest, then it would be possible to determine the final velocity. The equation we would use is:

vf^2 - vi^2 = 2ad

Where vf is the final velocity, vi is the initial velocity, a is acceleration (-9.8 m/s since it's free fall), and d is the displacement. So if it starts from rest, we have:

vf^2 - 0 = 2(-9.8)(-0.05)

vf = root(0.98)

vf=0.99 m/s

Keep in mind that the mass does not matter, all objects accelerate in free fall at 9.8 m/s^2 downwards.

Answer 2

The mass is a red herring.  In a free-fall situation, all you need is any two of time, distance, and acceleration due to gravity (a constant of 9.81 m/s^2).  You have distance and acceleration, so you find time with

t^2 = 2d/a

then velocity (average velocity, actually) = distance/time.

A more precise formula for velocity is vf^2 (final velocity squared) = vi^2 (initial velocity squared - in this case it would be zero) + 2ad.

Easier to read:  vf^2 = vi^2 + 2ad

Make sure to convert distance to 0.05 m since standard unit for velocity is m/s.

Answer 3

an object that weighs 80 grams that is falling is subject to acceleration due to gravity (9.81 m/s^2).  Assuming no friction, mass will not have any impact on your answer.

Using basic equations of kinematics:

v^2 = v(0)^2 + 2*a*d

v^2 = 0 + 2 * (9.81m/s^2) * .05m

v^2 = 0.4905 m/s

v = 0.7 m/s

Answer 4

You can do it if you know the force being applied to it or the acceleration.

I presume that the object is falling towards the earth and is acted upon only by gravity. As you should know, all objects falling due to gravity accelerate at the same speed. So, the mass does not really matter. All that matters is the acceleration. Acceleration due to gravity is always 9.8 m/s^2. The equation for distance that a falling object travels is d=vt+at^2, where v is the initial velocity and a is the acceleration and t is the time. As no initial velocity is given, it is safe to assume that the initial velocity is 0. Now just plug in the values and solve the equation.

Answer 5

cant .. unless we know the time...

Answer 6

you cannot do this.

Mass is not necessary because all falling bodies fall with the same acceleration. A bowling ball will hit the ground at the exact same time as a golf ball when dropped from the same height at the same time.

You do know the acceleration because anything that is falling is a projectile, and the acceleration due to gravity is -9.8m/sec^2.  It is negative to represent the direction of the acceleration (down).

Are you looking for the initial velocity or final velocity?  after falling 5cm, the velocity will have changed because things speed up as they fall, due to the acceleration from gravity.  

Basically, you need to know this:

d=v*t.  if you know the distance traveled and the time it took, you can find the velocity.

vf = vi + a*t.  you need the time for this one too.  then you need the initial velocity or final velocity to solve for the other one.  a = 9.8

d = vi*t+1/2*a*t^2.  You have the distance, then you need the time to find the initial velocity.  a = 9.8.

d = 1/2(vi +vf)*t.  once again: you need the time.  you have the distance, and you'll need either the initial velocity or final velocity to find the other one.

vf^2 = vi^2 +2*a*d.  this is the only way you can do it without knowing the time.  but you need the initial velocity or the final velocity to solve for the other one.

You can however find the force.  F = m*a so the force the object will experience after falling 5 cm is (.08 kg)(.05 m) = .004 N

Answer 7

well I think this formula can...

but here it did not use the mass... sorry... but I hope it helps...

vf= (square root of...) 2(d)(g)

vf is final velocity

d is distance

g is gravitational pull of earth which is constant= approximate of 10 m/s

Given:

d= 5m

g= approx. 10 m/s

vf= (square root of...) 2(5)(10)

vf= (square root of...) 100

the square root of 100 is...

10

vf= 10m/s

I hope its correct...