Hey everyone! Just wanted to point out a silly mistake. In Part B, at 10:43, the answer should be ax = -5.80 m/s^2 instead of -5.60 m/s^2. The work and the process is correct, I must have just put it into the calculator wrong. Study hard! 😃
Remember it is different for wheels! static friction opposing the motion for a wheel has downward directoin at the point of contact with surface (in order to have rolling without slipping, we have only mue s not mue k)
This problem is tricky. You actually have to add the static friction force and the x work of gravity. This is because at the start of the problem it says the car it is heading down the hill. So getting a negative acceleration makes little sense. Other than that very good video. Just add the two forces or else you will get the wrong answer.
for part A, the class solution manual added the two forces instead of subtracting resulting to an answer of 10.8 m/s2. I am confused on which is correct. Personally I think since acceleration and friction are in opposite directions we should subtract agreeing with your answer.
Your reasoning is correct! Since the w value is in the positive x-direction, it has to be positive and since the Fs is in the negative x-direction, it has to be a negative value. The format in the video is correct. Hopefully this helps!
Hi there! I see what you're asking, but in this case, the weight component along the slope (which is wy) is already accounted for by using sin(6°), while the weight component perpendicular to the slope (which is Fn) uses cos(6°). So to find the normal force (Fn), it's wy * cos(6°), not -wy/cos(6°). The negative sign usually represents direction, but here we’re just focusing on the magnitude for Fn. The formula stands in the video. Hope that clears it up!
The weight of an object always points DIRECTLY DOWNWARD. Since I took the plane of the slope to be the x-axis, the hypotenuse of the triangle that was created would be w. Study hard!
I am wondering about the backward friction force. The text says there is no slipping. But the only way to get a backward braking force on the car from the ground is to lock the wheels. Your calculations are based on that. A grave misunderstanding from you about basic physics.
Hey everyone! Just wanted to point out a silly mistake. In Part B, at 10:43, the answer should be ax = -5.80 m/s^2 instead of -5.60 m/s^2. The work and the process is correct, I must have just put it into the calculator wrong. Study hard! 😃
Remember it is different for wheels! static friction opposing the motion for a wheel has downward directoin at the point of contact with surface (in order to have rolling without slipping, we have only mue s not mue k)
This problem is tricky. You actually have to add the static friction force and the x work of gravity. This is because at the start of the problem it says the car it is heading down the hill. So getting a negative acceleration makes little sense. Other than that very good video. Just add the two forces or else you will get the wrong answer.
wait for it to be decelerating doesn't that mean the car wheels must be slipping?
for part A, the class solution manual added the two forces instead of subtracting resulting to an answer of 10.8 m/s2. I am confused on which is correct. Personally I think since acceleration and friction are in opposite directions we should subtract agreeing with your answer.
Your reasoning is correct! Since the w value is in the positive x-direction, it has to be positive and since the Fs is in the negative x-direction, it has to be a negative value. The format in the video is correct. Hopefully this helps!
How do you know when to use SIN vs. COS?
in the step finding Fn shouldn't w= -wy/cos6 ??? because you multiple the w to get it out of the denominator then divide both sides be cos 6?
Hi there! I see what you're asking, but in this case, the weight component along the slope (which is wy) is already accounted for by using sin(6°), while the weight component perpendicular to the slope (which is Fn) uses cos(6°). So to find the normal force (Fn), it's wy * cos(6°), not -wy/cos(6°). The negative sign usually represents direction, but here we’re just focusing on the magnitude for Fn. The formula stands in the video. Hope that clears it up!
thank you so much this was super super helpful!!!!!!!!!
You got it, Stephanie! Glad this video has helped you in your Physics class! Keep working hard and help us spread the word! 😀
I used this tutorial to solve a similar question with different values and got every single answer part wrong...lol
For part A, shouldn't the hypotenuse be -wy, not w? And the adjacent is w, not -wy
The weight of an object always points DIRECTLY DOWNWARD. Since I took the plane of the slope to be the x-axis, the hypotenuse of the triangle that was created would be w. Study hard!
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Glad this video helped, Mahammed! 😀
I am wondering about the backward friction force. The text says there is no slipping. But the only way to get a backward braking force on the car from the ground is to lock the wheels. Your calculations are based on that. A grave misunderstanding from you about basic physics.