Physics 8 Work, Energy, and Power (22 of 37) Box pushed up a Frictionless incline

This six part physics lecture series will cover the concepts of Work and Energy.

Problem Text:
A box with a mass of 20kg is pushed 100m up a frictionless incline that makes an angle of 40 degrees with the horizontal. The box moves slowly at a constant speed. How much work did it take?

[solomonwang]

my left ear liked it, my right ear couldnt hear it

[Urielren]

What would happen if the given mass of the box was in Newtons? could I plug it into the equation just like you did by multiplying it with the other factors or must it be converted to Kg?

[perry]

of all of the physics tutorials i've watched on youtube, you're by far the easiest to follow and the best with conceptualizing (for me at least), thank you!

[albertopoli]

At the beginning: the F (in red) must be equals to mgsinθ, the two forces have the same value but in opposite, so how is possibile moving the box? Or the box already had speed? Many thanks

[shobhanasingh]

Exactly, I was so confused while solving such a numerical that if the force is equal to mgsin theta how wud d box even move!
Thanks a lot!

[kamvasco]

you do much work everyone lets get him to 1 mill subscribers

[YashRaj-xcuw]

What if the acceleration with which the block is going up the wedge would be non zero??
What changes would it make to the equation of work done??
Please reply🙏

[primsiren]

Can somebody tell me why i get the following problem wrong?

On a fairground ride, the track descends by a vertical drop of 55m over a distance of 120m along the track. A train of mass 2500kg reaches a speed of 30m/s at the bottom of the descent after being at the top.

a) find the loss of GPE (answer = 1347500J)
b) find the gain in KE (answer = 1125000J)
c) find the average frictional force on the train during the descent

I get 1685.56N for c) but the book says 1830N

i do w=fs, w=222, 500 and s = 5 SQRT(697) to get f = 1685.56, but the book does 222, 500 / 120, but surely the train travels 5 SQRT(697)m not 120m ?

[jeremykemp]

How is this expressed on the calculator when typing in the cosine? I pressed sine and 40 but my answer was not the same as yours. I get 125.98

[idkwiwmhtb]

Honestly thank u so much u just cleared 4 months of confusion

[thailandfutsal]

Why don t think the work from. Mgsin seta

[lydiaaksas]

why didn't we add the KE and the PE to find the W ?

[christopherwilkins]

These videos are definately clearing up some concepts I was confused on. I think I'm going to start watching your videos on the chapter subjects before I delve into the book material. I keep having misconceptions in the conclusions I come to after reading through the chapters. I see massive redundencies in my notes now that I'm actually getting a grasp on this subject lol. Thank You.

[pp]

So for frictionless slopes its just mgh

[mehedimisson]

Thank you Sir . Your lecture about this topic helped me much more than the classes I had in my college !

[iheartqueso]

You should add links to the next video in a sequence to your videos. Just a suggestion. 

[weeborghini]

My left ear is smarter than the right one

[juansutandyo]

What if the speed of the block increased? Would the work done on the block be the sum of the change in both potential and kinetic energy?

[miscellanicole]

I've watch 3 of your Mechanics series and I truly appreciate your clear, logical explanations and your time. Your tutorials have helped me immensely.

[albertopoli]

If I push the block with a Force greater then mgsinθ, I have a Fnet and then an acceleration. In this case have I variation of KE? Many thanks