Posted by michelle quendarsv on Saturday, November 20, 2010 at 5:26pm.

Posted by michelle quendarsv on Saturday, November 20, 2010 at 3:55pm.

if it takes 726 watts of power to move a mass 36 meters in 14 seeconds, what is the mass?

i really need like, step by step help please? asap.
thanks, michelle .
physics - bobpursley, Saturday, November 20, 2010 at 4:06pm
power= work/time= mass*g*distance/time

mass= power*time/distance*g

physics - michelle quendarsv, Saturday, November 20, 2010 at 4:24pm
so... would it be like,
726 x 14 / 36 ?
physics - bobpursley, Saturday, November 20, 2010 at 6:08pm
no, what happened to g (9.8m/s^2) in the denominator?

physics - michelle quendarsv, Saturday, November 20, 2010 at 6:40pm
but where did you get 9.8m/s2?

He is assuming that you are moving the mass up against gravity. g = 9.8 m/s^2

then force up = m g = 9.8 m

If you are moving it horizontally and there is no friction and it is stopped at the start, that is another problem entirely.
It has zero kinetic energy at the start and we need to find the KE at the end to find how much work is done.
we need the acceleration
36 = (1/2) a (14)^2
a = .367 m/s^2
then
v = a t = .367 *14 = 5.14

then (1/2) m (5.14)^2 = 726*14

However I suspect that the way bobpursley told you is what your teacher wants.

That's a lot of work...

umm, it says nothing about "moving up against gravity"

but if you say so... thanks, i guess.

can you give me another example with this question

-What is the mass of an object if it took 270 J of work to move it 15 meters?

9.8 is g

If moving it up then
F = m g
F * distance = work = 15 m (9.8) in Joules
so
270 = 15 * m * 9.8
m = 270 / (15*9.8)

To solve this problem, you need to use the formula for power and rearrange it to solve for mass. The formula for power is:

power = work / time

In this case, the work done is equal to the force required to move the mass multiplied by the distance traveled. The force required to move the mass is equal to the mass multiplied by the acceleration due to gravity (g). So, we can rewrite the formula for power as:

power = (mass * g * distance) / time

To solve for the mass, you need to rearrange the formula and isolate the mass variable. The formula becomes:

mass = (power * time) / (g * distance)

Now you can substitute the given values into the formula. The power is given as 726 watts, the time is given as 14 seconds, and the distance is given as 36 meters. The value of acceleration due to gravity (g) is 9.8 m/s^2.

So, plugging in the values into the formula:

mass = (726 * 14) / (9.8 * 36)

Now you can calculate the mass. By performing the multiplication and division, you will obtain the mass in units of kilograms.

To answer your question about where the value of 9.8 m/s^2 comes from, it is the standard value for the acceleration due to gravity on Earth. The value 9.8 m/s^2 represents the rate at which objects accelerate towards the Earth under the influence of gravity.