a. If you press a book flat against a vertical wall with your hand, in what direction is the friction exerted by the wall on the book?
b. A crate is shitting in the center of a flatbed truck. As the truck accelerates to the east, the create moves with it, not sliding on the bed of the truck. In what direction is the friction force exerted by the bed of the truck on the crate?
Please also explain why. Thank you.
2007-10-20 13:32:29 · 7 answers · asked by Anonymous in Science & Mathematics ➔ Physics
(a) If you press a book flat against a vertical wall with your hand, the friction exerted by the wall on the book is in vertical upward direction because the book is at rest under the action of two forces, weight and friction.As resultant is zero, the weight downwards is balanced by friction upwards
(b)As the truck accelerates to the east, the create moves with it, not sliding on the bed of the truck. and accelerates towards east , the friction force exerted by the bed of the truck on the crate is towards east
The weight of crate is balanced by normal reaction and acceleration of crate towards east is due tom friction only, hence friction has to be east
friction accelerates crate towards east
2007-10-20 15:25:53 · answer #1 · answered by ukmudgal 6 · 0⤊ 0⤋
If the book is not moving against the wall, friction is not doing anything. Friction only exists when something is moving against something.
The friction is pulling the crate east. Because of inertia, the crate would rather stay at the same velocity. If the truck accelerates to the east, the crate would not accelerate with the truck, and would instead be left behind. However, it moves with the truck, meaning that there is a force pushing it in that direction. That force is friction.
2007-10-20 20:43:35 · answer #2 · answered by lomelinde 3 · 0⤊ 0⤋
a. Upward. The book is not falling (or rising) so there is no net vertical force on the book. Something must cancel the -mg force of gravity, and friction is the only other external force with a vertical component.
b. Is that "sitting" or "shifting"? Only "sitting" actually works, and in that case the answer is east because the frictional force is accelerating the box to move eastward with the truck. For the question as asked, I have no answer.
2007-10-20 21:17:56 · answer #3 · answered by husoski 7 · 0⤊ 0⤋
a/ the friction is caused by your hand pushing the book towards the wall.Any friction by the wall would therefore be up(to counteract gravity), and out towards yourself(an opposing force).
b/ That's no way for a crate to make itself popular!.Anyway the friction exerted by the truck will be forwards to the crate as the inertia of the crate will make it try to slide backwards.
2007-10-20 20:49:03 · answer #4 · answered by Mika K 4 · 0⤊ 0⤋
a) friction by the wall on the book is acting in the upwards direction. the friction force here opposes the force of gravity on the book (which acts downward)...
b) friction on crate by truckbed is to the east.. the friction opposes the force trying to send the crate off the truck due to the accelertion
2007-10-20 20:41:16 · answer #5 · answered by Anonymous · 0⤊ 0⤋
a) vertical since friction is the force that opposes the movement of two bodies as they move relevant to each other, so since your forcing the book on the wall one way that's the direction the force is coming from.
b) it moves east with the truck since no opposing greater force is acting on it. it's like when you sit in a chair on a bus. your sitting still but the bus is going 45 miles an hour.
2007-10-20 20:39:29 · answer #6 · answered by Anonymous · 0⤊ 0⤋
Why is the crate "shitting" in the truck - is it not potty trained?
2007-10-20 20:35:08 · answer #7 · answered by ParisAngel123 1 · 1⤊ 0⤋