Solving D'Alembert's Equation: Homework Help

[Vancurt]

Homework Statement

Hey, this is the first time i have ever done this and i like to know how to solve it.

A car with a mass of 1350kg is tested by having it accelerated up a road with a slope of 1 in 5,increasing in speed from 2.5 to 12 m/s,covering a distance of 100m, agaisnt a frictional force of 750 N.

Determine:

The tracktive effort between driving wheels and the road surface.

The work done during period of the acceleration
The average power developed.

The Attempt at a Solution

My first time doing tracktive efforts and Alemberts equation, but from what i gathered on the internet:

My tutor does not seem to understand English either, we all asked for tips and guidance, he replied with 'ask your friends'.

100x1/5 =20m

1350x9.81x20= 264870.

Don't ask where the 9.81 came from, i saw quite a few answers with it in so i guessed.

 

[PhanthomJay]

You need to understand kinematics, Newton's laws, free body diagrams, Work, and/or energy. g = 9.81 m/s^2, the acceleration of gravity. Please make an attempt.

 

[Vancurt]

Ok here is my attempt, possibly all wrong.

I guessed the tracktive effort is 2100.2

I got this by looking at the D'Alembert's equation:

Tracktive effort = gravitational force + inertia resistance + frictional resistance.

For Gravitational force, i put 1350 as that is mass and a force, the inertia resistance 1 over 5 as that is the resistance going up a slope and for the frictional force 750 because it says so.

Therefore 1350 + 1/5 + 750 = 2100.2

B) is work done so the equation: force x Distance = 750 x 100 = 75000

C) Average power i looked upon the internet for the equation which is: Integral power over time divided by time interval.

So just grasping at straws here: 75000 divided by 1/5 = 375000.

 

[PhanthomJay]

Ok here is my attempt, possibly all wrong.

I guessed the tracktive effort is 2100.2

I got this by looking at the D'Alembert's equation:

Tracktive effort = gravitational force + inertia resistance + frictional resistance.

Are you being asked to use D'Alembert's equation? It has merit for certain problems, but in general, stick with Newton's 2nd Law.

For Gravitational force, i put 1350 as that is mass and a force,

1350 kg is the mass...its weight is 1350(9.81) or approximately 13,200 N... but you should be looking at the component of the weight acting down the plane

the inertia resistance 1 over 5 as that is the resistance going up a slope

you have a wrong definition of the inertia force...it is mass times acceleration (ma)

and for the frictional force 750 because it says so.

, acting down the plane

Therefore 1350 + 1/5 + 750 = 2100.2

rework the first 2 terms

B) is work done so the equation: force x Distance = 750 x 100 = 75000

the net work done is the work done by all forces , that is, the work done by the net force acting on the car, if this is what the problem is asking

C) Average power i looked upon the internet for the equation which is: Integral power over time divided by time interval.

So just grasping at straws here: 75000 divided by 1/5 = 375000.

really grasping...average power is force times average speed///