- #1
Stephanus
- 1,316
- 104
Dear Physics Forum,
I really don't understand the concept of watt and Newton.
I have two questions, perhaps someone can explain it to me.
=======================================================
Case 1:
If a one Newton force is applied to a one kg rocket in space with no or very little effect of gravity, for ...
A. 10 seconds, it will travel (1/2 x a x t^2 = 1/2 x 1 x10^2 = 50) 50 metres, it has consumed 50 joules, so its power is 5 watt.
B. 20 seconds, it will travel 200 metres, it consumes 200 joules, power is 10 watt.
C. 30 seconds, 450 metres, 450 joules, 15 watt
It seems that the power is increasing with each passing time(second). Its energy consume is not constant, but accelerating with each passing time.
Question1: Is that true?
======================================================
Case 2:
Before I ask, I would like to insert some equations here.
E = P.t (energy is power x time, second)
E = F.d (energy is force x distance, metre)
F = M.a (force is mass x accel)
d = 1/2 a.tt (dist is accel x time squared)
P.t = F.d
E = (F) x (d)
E = (M x a) x (1/2 a x tt)
E = 1/2 M x aa x tt
aa = 2E/M/tt
a = sqrt(2E/M)/t
F = M x sqrt(2E/M)/t = sqrt(2EM)/t
d = 1/2 a.tt = sqrt(1/2 x E/M)/t x tt = sqrt(1/x2 x E/M) x t
Note:
F.d = sqrt(2EM)/t x sqrt(1/2 x E/M) x t = sqrt(2 x 1/2 x EE) x t / t = sqrt(EE) = E
F.d is of course (E)nergy
--------------------------------------------------------------------------------
A one kg rocket in space (no gravity) having a one watt power. Assuming it has a very, very efficient fuel, so the fuel mass loss is negligible.
A. After 2 seconds, its energy consume is 1 watt x 2 seconds = 2 Joule.
Its Force will be 1 Newton, its distance has to be 2 metres, 1 Newton x 2 metres = 2 joule
B. After 8 seconds, its energy consume is 8 joules
Its Force is 0.5 Newton x its distance is 16 metres = 8 joules
C. After 32 seconds , 32 joules
Force: 0.25 Newton, distance: 128 metres.
It seems with each passing time the force is diminishing.
Is that true?
Note: It will take 5.6 billion years to push it near the speed of light
11 billion years = twice the speed of light? But that's another question for relavity I think.
======================================================
Conclusion:
1. If the force is constant, does the power increase?
2. If the power is constant, does the force decrease?
Thanks for any answer.
Peace on earth
Steven
I really don't understand the concept of watt and Newton.
I have two questions, perhaps someone can explain it to me.
=======================================================
Case 1:
If a one Newton force is applied to a one kg rocket in space with no or very little effect of gravity, for ...
A. 10 seconds, it will travel (1/2 x a x t^2 = 1/2 x 1 x10^2 = 50) 50 metres, it has consumed 50 joules, so its power is 5 watt.
B. 20 seconds, it will travel 200 metres, it consumes 200 joules, power is 10 watt.
C. 30 seconds, 450 metres, 450 joules, 15 watt
It seems that the power is increasing with each passing time(second). Its energy consume is not constant, but accelerating with each passing time.
Question1: Is that true?
======================================================
Case 2:
Before I ask, I would like to insert some equations here.
E = P.t (energy is power x time, second)
E = F.d (energy is force x distance, metre)
F = M.a (force is mass x accel)
d = 1/2 a.tt (dist is accel x time squared)
P.t = F.d
E = (F) x (d)
E = (M x a) x (1/2 a x tt)
E = 1/2 M x aa x tt
aa = 2E/M/tt
a = sqrt(2E/M)/t
F = M x sqrt(2E/M)/t = sqrt(2EM)/t
d = 1/2 a.tt = sqrt(1/2 x E/M)/t x tt = sqrt(1/x2 x E/M) x t
Note:
F.d = sqrt(2EM)/t x sqrt(1/2 x E/M) x t = sqrt(2 x 1/2 x EE) x t / t = sqrt(EE) = E
F.d is of course (E)nergy
--------------------------------------------------------------------------------
A one kg rocket in space (no gravity) having a one watt power. Assuming it has a very, very efficient fuel, so the fuel mass loss is negligible.
A. After 2 seconds, its energy consume is 1 watt x 2 seconds = 2 Joule.
Its Force will be 1 Newton, its distance has to be 2 metres, 1 Newton x 2 metres = 2 joule
B. After 8 seconds, its energy consume is 8 joules
Its Force is 0.5 Newton x its distance is 16 metres = 8 joules
C. After 32 seconds , 32 joules
Force: 0.25 Newton, distance: 128 metres.
It seems with each passing time the force is diminishing.
Is that true?
Note: It will take 5.6 billion years to push it near the speed of light
11 billion years = twice the speed of light? But that's another question for relavity I think.
======================================================
Conclusion:
1. If the force is constant, does the power increase?
2. If the power is constant, does the force decrease?
Thanks for any answer.
Peace on earth
Steven