Calculating Weight Component: 46 Degree Slope & Constant Speed | Homework Help

[ishotbambi]

Homework Statement

A simple one mark question which is doing my head in.
'There is a lorry traveling up a slope. Angle of slope is 46 degress with the horizontal and the weight of the lorry is 240000N. A resistive force of 1200N down the slope acts on the lorry as it travels up the slope at a constant speed of 15 meters per second.
Q: Show that the component of the weight down the slope is 20000N

Homework Equations

The Attempt at a Solution

I simply can't get my head round it. Why would the weight change? Wouldn't weight remain constant whatever the lorry is doing?

 

[Tzim]

You are right the weight doesnot change.But it has 2 componets.One opossite to the direction of the movement of the lorry an one vertical to the slope.
So by the pythagoras theorem root(Wx^2 + Wy^2)=W
where Wx is the the componet of the weihgt parallel to the slope and Wy the one vertical to the slope

 

[Tzim]

Take a look of what i mean.

 

[Tzim]

I am sorry i probably misunderstood your question

 

[Tzim]

Did you cinsider the case tha the question is wrong.The weight cannot change.Wx=240000*sin46