- #1
badsanta010
- 7
- 0
Hi
I have been working on this problem now for a good few weeks and I think I am nearly there just need help on the last bit.
The Question:
A car of mass 1200kg accelertaes from 2.5 to 5.0 ms while traveling up a slope of 1in 10, through a distance of 60m. If resistance to motion is 105N determine using both an energy method and D'Alemberts principle
a) The tractive effort F required
b) Work done
c) average power required to accelerate load
What I have done so far.
Part a)
I worked out acceleration using a=(v^2 - u^2 ) / 2s giving me a= 0.15625 m/s
Then using m x a to work out inertia resistance = 187.5N
I then worked out the angle ( bottom left of traingle ) by using slope of 1 in 10 = 0.1 and doing tan-1(0.1 to give 5.71 degress
I then worked out the gravitational force m x g x sin pheta ( 1200 x 9.81 x sin(5.71 )
This gave 1171.357N
Adding these with my original resistance to motion gave me a tractive effort of 1463.857139N
Part a) done hopefully
Part b)
Work done = f x s
1463.857139 x 60 = 87831.42834 Nm
Part c) Power = work done / time taken
Time taken = change in velocity / acceleration
2.5/0.15625 = 16 secs
Power = 87831.42834 / 16 = 5489.4642
I divided this my distance of 60m to give 91.49107 Nms
This is where I am stuck I understand I need to use conservations of energy which mean working out PE and KE.
Intial KE
KE= 1/2 m x v^2
600 x 2.5^2 = 3750J
Final KE
600 x 5^2 = 15000
Give me a change in KE of 11250
And that as much as I can do.
Sorry for it being quite long but I really want to get through this question. Any input is greatly appreciated. Thanks
I will attached a picture of a diagram that also comes with the questions
Thanks again
I have been working on this problem now for a good few weeks and I think I am nearly there just need help on the last bit.
The Question:
A car of mass 1200kg accelertaes from 2.5 to 5.0 ms while traveling up a slope of 1in 10, through a distance of 60m. If resistance to motion is 105N determine using both an energy method and D'Alemberts principle
a) The tractive effort F required
b) Work done
c) average power required to accelerate load
What I have done so far.
Part a)
I worked out acceleration using a=(v^2 - u^2 ) / 2s giving me a= 0.15625 m/s
Then using m x a to work out inertia resistance = 187.5N
I then worked out the angle ( bottom left of traingle ) by using slope of 1 in 10 = 0.1 and doing tan-1(0.1 to give 5.71 degress
I then worked out the gravitational force m x g x sin pheta ( 1200 x 9.81 x sin(5.71 )
This gave 1171.357N
Adding these with my original resistance to motion gave me a tractive effort of 1463.857139N
Part a) done hopefully
Part b)
Work done = f x s
1463.857139 x 60 = 87831.42834 Nm
Part c) Power = work done / time taken
Time taken = change in velocity / acceleration
2.5/0.15625 = 16 secs
Power = 87831.42834 / 16 = 5489.4642
I divided this my distance of 60m to give 91.49107 Nms
This is where I am stuck I understand I need to use conservations of energy which mean working out PE and KE.
Intial KE
KE= 1/2 m x v^2
600 x 2.5^2 = 3750J
Final KE
600 x 5^2 = 15000
Give me a change in KE of 11250
And that as much as I can do.
Sorry for it being quite long but I really want to get through this question. Any input is greatly appreciated. Thanks
I will attached a picture of a diagram that also comes with the questions
Thanks again