i dont know why i am having so much trouble grasping these concepts, like i understand what velocity, acceleration, force etc is but when it comes to problems involving these concepts (not even math problems) i dont even know. all the answers seem right. for example...constant velocity of 256m/s? is that even possible if it is moving at a constant velocity, because i thought constant velocities had a net force of 0. please halp
also, If a block is moving to the left at a constant velocity, that means there is exactly 1 force acting on it right?
An object accelerates if it has unbalanced forces acting on it. If an object is at rest (0 m/s) it is still moving at a constant velocity, because the velocity is not changing. Think of it this way: You are in space. There is no friction. You push a ball, and it glides off into space. After the ball leaves your hand, you are no longer imparting a force on it. Yet, the ball is still moving, and not slowing down or speeding up because there are no forces acting on it. In an ideal environment, force is only needed to start or stop motion, or to change velocity. To address your second question, an object moving at a constant velocity can have any number of forces acting on it, as long as the horizontal and vertical components cancel out to 0.
ok, so in the first question the answers would be all of the choices with the same numbers of Newtons right? (2 N; 2 N, 200 N, 200 N etc)
Those, and the option of 2,2,4. You could have both 2N forces acting in one direction and the 4N force acting in another.
Trusay! Epic. I have another question though... Two forces, of magnitude <span style="margin:0px;"><span style="margin:0px;"><span style="margin:0px;font-size:16px;"><span style="margin:0px;"><span style="margin:0px;"><span style="margin:0px;">4<span style="margin:0px;">N</span></span></span></span></span></span></span> and <span style="margin:0px;"><span style="margin:0px;"><span style="margin:0px;font-size:16px;"><span style="margin:0px;"><span style="margin:0px;"><span style="margin:0px;">10<span style="margin:0px;">N</span></span></span></span></span></span></span>, are applied to an object. The relative direction of the forces is unknown. The net force acting on the object __________. select all that apply... cannot have a magnitude equal to 5 N cannot have a magintude equal to 10 N cannot have the same direction as the force with magnitude 10 N must have a magnitude greater than 10 N Sooo i'm assuming i should select A, B and D?!
Incorrect. The largest resultant possible is 14, if the forces act concurrently (at an angle of 0) and the smallest is 6 (at an angle of 180). Therefore, D is false. C is true, as the resultant force acts in the same direction as the 10N force if both forces act in the same direction. I believe A, and B are true.
if i was just asking for the answers without the why....yeah. but i want to know why this is so confusing! we havent learned anything about angles yet heh..so how do i determine the net force? it said direction unknown...how does direction come into play ?
I made a boo-boo. B should be correct. You use the angle between the forces to determine the resultant, which is essentially both forces combined into one. To do this you need to use trigonometry. The direction of forces relative to each other can increase or decrease the magnitude of the resultant and change the direction. Like I said earlier, if you have both acting in the same direction, that maximizes the magnitude of the resultant. Opposite directions minimize it's magnitude. I'd suggest looking up KhanAcademy. They probably have a shit load of lessons on basic vector physics.
It looks like an online class to me. Unfortunately those usually have very limited materials to learn from. I took calc 3 and Diffeq. online and it was hell.
Oh, also some shameless promotion. Check out www.newtonianthinkers.com. I may or may not be affiliated with their mechanics book...
yepthey sure do good idea! thabks for the helpman yep online class....sucks. calc 3 and ODE online? FUCK. THAT. one more general question....if an object, like a car, is moving at a constant velocity (constant speedand direction), it is not accelerating, correct?
You're very welcome! And you're correct, with velocity AND direction constant. Something changing direction is accelerating even if it remains at the same speed.
its that time again....time for my physics homework....a question... talking about momentum... a bus and a bicyclist collide. the amount of force they exert on each other is equal due to newtons 3rd law...i understand this 3rd law quite well i believe. however, the tutorial online says the acceleration of the bus is very small compared to the acceleration of the cyclist....why!? i dont get that at all. the bus has way more mass even if it is going by chance the same speed, so shouldnt it have more momentum? or am i confusing a few different things.