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?
physics - Damon, Saturday, November 20, 2010 at 7:27pm
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.
physics - Damon, Saturday, November 20, 2010 at 7:29pm
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.
physics - michelle quendarsv, Saturday, November 20, 2010 at 8:03pm
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?
Physics - Damon, Saturday, November 20, 2010 at 8:15pm
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)
Physics - michelle quendarsv, Saturday, November 20, 2010 at 8:28pm
Okay, thank you...
I have another question
If an object has a mass of 47 kg and it is moved 27 meters in 60 seconds, how much power was used?
(also, would this also include the 9.8 from g?)
Thanks.
To find the power used, we can use the formula:
Power = Work / Time
The work done on an object is equal to the force applied multiplied by the distance traveled. In this case, since we are not given the force directly, we need to calculate it using the formula:
Force = Mass × Acceleration
Acceleration can be found using the formula:
Acceleration = Distance / Time^2
Using these formulas, let's calculate the power used step-by-step:
Step 1: Calculate the acceleration.
Acceleration = Distance / Time^2
Acceleration = 27 m / (60 s)^2
Acceleration = 27 m / 3600 s^2
Acceleration = 0.0075 m/s^2
Step 2: Calculate the force.
Force = Mass × Acceleration
Force = 47 kg × 0.0075 m/s^2
Force = 0.35 N
Step 3: Calculate the work done.
Work = Force × Distance
Work = 0.35 N × 27 m
Work = 9.45 J
Step 4: Calculate the power used.
Power = Work / Time
Power = 9.45 J / 60 s
Power ≈ 0.158 W
So, approximately 0.158 watts of power were used to move the object. And no, this calculation does not include the 9.8 from g since we are not moving the object against gravity.
To find the power used, we can use the formula:
Power = Work / Time
In this case, the work done is related to the force required to overcome gravity, since the object has a mass of 47 kg. The force required to overcome gravity is given by:
Force = mass * acceleration due to gravity
Force = 47 kg * 9.8 m/s^2 = 461.6 N
The work done against gravity is equal to the force multiplied by the distance traveled:
Work = Force * distance = 461.6 N * 27 m = 12451.2 J
Now, let's substitute the values into the power formula:
Power = Work / Time = 12451.2 J / 60 s = 207.52 watts
Therefore, the amount of power used is 207.52 watts. And yes, 9.8 m/s^2 is the acceleration due to gravity, so it should be included in the calculation.