Physics: Work. Conservation of energy (1)

[hussansohaib]

thank u very much for very helpful lectures...

[sarah29172]

you rule freelanceteach!!!

[Clipster15]

You state that a perpendicular force to its motion does no work which makes sense by the definition of work. But if the force is originally perpendicular and causes a change in direction, then the moment after that, it is no longer perpendicular to the motion and does do work. Correct? The only way that no work is done continuously is if the force is kept perpendicular to the motion (e.g a circle path) or the particle/mass resists the perpendicular force, right?

[NDGirl1100]

Wow!!! Thank you!

[malimalinche1]

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[Elricky124]

Thank you very much! I enjoy listening to watching your videos. It dimystifies a lot of the concepts of physics.

[DTechEdu]

You are amazing ..thanx so much for your lectures!

[WongeneKIM]

Thank you for your lectures!

[MedicalSchoolFinder]

wow

[sameerxD]

at 4:10, when he works with force and velocity vectors, those speed up, slow down, and change direction, really define sign of work. If the vectors are in the same direction, work is positive. if vectors are in the opposite direction, it's negative. if they're perpendicular, W = 0. It's called the vector dot product, basically, | F | x | delta r | x cos (angle between the vectors). Cos(0) = 1, cos(180) = -1, Cos(90) = 0.

[LLiimmzz]

THANK YOU SOOO MUCH FOR THIS 

[abeness88]

I THINK THE GIRL THAT ASKED THE QUESTION AT 5:40 TIME WAS REFERRING TO CHANGE IN VERTICAL DIRECTION DOES DECREASE SPEED. IF YOU THROW SOMETHING UP VERTICALLY IN THE AIR LIKE A BALL...IT WILL REACH A POINT AT ITS HIGHEST PEAK...STOP AND COME BACK DOWN...WHERE CHANGING DIRECTION IN THIS CASE...DOES CHANGE YOUR VELOCITY.

[CitizenofDystopia]

@abeness88 I don't believe so. All the force would be doing is changing the direction. Another force (in this case gravity) would change the velocity. You don't see objects just going horizontally and then gravity randomly pushing them vertically in the upward direction.