Forces, Vectors and Friction
What I have learned:
*Force Earth= the force exerted by the Earth that is pulling an object vertically downward
-> Force Earth pulls down at an object at 9.8m/s^2
*Force Earth= the force exerted by the Earth that is pulling an object vertically downward
-> Force Earth pulls down at an object at 9.8m/s^2
*Force Ground= the force exerted by the ground that is perpendicular to the ground
*Force Normal= the perpendicular force to the surface
-> If the ground is horizontal= force ground is vertical, but if the ground is tilted at an angle= force ground is pointing 90 degrees perpendicular to the ground
*Force Normal= the perpendicular force to the surface
-> If the ground is horizontal= force ground is vertical, but if the ground is tilted at an angle= force ground is pointing 90 degrees perpendicular to the ground
-> It does not have to be specifically the ground. It is just the force of the surface. If I want to draw a force diagram of a cup on a table, the force of the surface is called Force Table.
*Force Net= Mass x Acceleration
*Newton= (Kilogram)(meters/second^2)
*1 Newton is 100 grams
*When finding forces, you can use sine, cosine, and tangent. Another way is to add vectors and to use trigonometry there too.
*Newton's First Law: An object at rest tends to stay at rest and an object in motion tends to stay in motion unless it is acted upon by an unbalanced force.
*Newton's Second Law: Force=mass x acceleration, acceleration=force/mass, mass=force/acceleration
*Newton's Third Law: For every action, there is an equal and opposite reaction.
-> For example, the amount of force you push on a wall is the same amount of force the wall pushes back on you.
-> Another example, the amount of force a truck applies to a small car when they collide is the same amount that the small car applies to the truck.
-> The drastic differences in the effects of the collision come from the fact that the two vehicles have different masses.
*Newton= (Kilogram)(meters/second^2)
*1 Newton is 100 grams
*When finding forces, you can use sine, cosine, and tangent. Another way is to add vectors and to use trigonometry there too.
*Newton's First Law: An object at rest tends to stay at rest and an object in motion tends to stay in motion unless it is acted upon by an unbalanced force.
*Newton's Second Law: Force=mass x acceleration, acceleration=force/mass, mass=force/acceleration
*Newton's Third Law: For every action, there is an equal and opposite reaction.
-> For example, the amount of force you push on a wall is the same amount of force the wall pushes back on you.
-> Another example, the amount of force a truck applies to a small car when they collide is the same amount that the small car applies to the truck.
-> The drastic differences in the effects of the collision come from the fact that the two vehicles have different masses.
Questions that I have & to discuss in class:
*I push a box and the box starts moving in the direction that I pushed it. From this situation, I want to make a force diagram of the box WHILE it is moving. When it is sliding across the ground, do I include the force from my push in the force diagram? Do I include an arrow from the force that I applied? Am I even still in the situation of the force diagram? No, I am not in the situation anymore while the box is moving. Therefore, the force diagram should only have the Earth force balanced with the ground force and a friction force pointing opposite to the direction of the motion. In another example, if I hit a tennis ball with a tennis racket and the tennis ball flies mid-air, what would be the motion map? The motion map will be the Earth force and probably the force from air resistance. One cannot exactly figure out an object's direction of motion from force diagrams in instances such as these.
*For Newton's First Law, if an object is in motion, it will remain in motion unless it it acted upon by an unbalanced force. The object's motion is in constant velocity (going the same speed and direction). But can the first law apply to objects moving in acceleration instead of velocity? For example, an object will continue falling (this is the "remain in motion part") until it is acted upon by an unbalanced force (which is the ground). Can the first law apply to objects accelerating or no?
*This question is a bit off topic but what does the area of an Acceleration v. Time graph show?
*The description of the normal force is too vague. What is the normal force? Normal force= perpendicular. What does this mean?
*Force Earth pulls down at an object at 9.8m/s^2. Do we make the 9.8m/s^2 negative because the direction is down? Depends on the situation. If the object is falling down in the negative direction (velocity increasing is the negative direction), then the acceleration is negative. If the object in thrown up into the air in the positive direction (slowing down in the positive direction), the acceleration is positive.
*For Newton's First Law, if an object is in motion, it will remain in motion unless it it acted upon by an unbalanced force. The object's motion is in constant velocity (going the same speed and direction). But can the first law apply to objects moving in acceleration instead of velocity? For example, an object will continue falling (this is the "remain in motion part") until it is acted upon by an unbalanced force (which is the ground). Can the first law apply to objects accelerating or no?
*This question is a bit off topic but what does the area of an Acceleration v. Time graph show?
*The description of the normal force is too vague. What is the normal force? Normal force= perpendicular. What does this mean?
*Force Earth pulls down at an object at 9.8m/s^2. Do we make the 9.8m/s^2 negative because the direction is down? Depends on the situation. If the object is falling down in the negative direction (velocity increasing is the negative direction), then the acceleration is negative. If the object in thrown up into the air in the positive direction (slowing down in the positive direction), the acceleration is positive.
Points from discussion:
*Friction can prevent or go against motion.
*One method to find friction is that if an object it moving at a constant velocity, then you know the force of the object moving is equivalent to the force of the friction.
*You can change the axes on the force diagram to be parallel to the surface so that it will be easier to find the vectors.
*One method to find friction is that if an object it moving at a constant velocity, then you know the force of the object moving is equivalent to the force of the friction.
*You can change the axes on the force diagram to be parallel to the surface so that it will be easier to find the vectors.
*You can "split" a diagonal force into its horizontal and vertical vectors (think Algebra).
Reflection:
When it comes to finding forces by adding and subtracting vectors, my understanding is still a bit hazy. However, when I use trigonometry, I understand that and I can solve the practice problems. Seeing a force diagram and using trig with to solve for the forces makes sense since I am a visual person. What I do not understand about vectors is the fact that although I can add and subtract them, I cannot find some the angles. When I try the vector method, I always only find one angle and the other angles I cannot solve.
-> My resolution: I am going to go to physics during lunch and work on vectors (and possibly practice using the force tables).
With F=ma, I like it a lot. I like doing math in physics so it's not a big challenge.
The actual challenges that I have are doing lab work/experiments and trying to derive conclusions from our data. I am not a handy person, so running experiments are always difficult because I make many errors. Also, during whiteboard discussions, when the class has to come to some sort of conclusion with the data, I have a hard time drawing that conclusion. I can find the answers when I am guided with help, but trying to come up with the equation/connection/pattern myself, that is very difficult.
-> My resolution: I will pay closer attention to detail, whether that be during labs or during the whiteboard discussion. I think that if I am more careful and attentive, I'll be able to make less errors and I'll have an easier time drawing those equations, connections or patterns.
Reflection:
When it comes to finding forces by adding and subtracting vectors, my understanding is still a bit hazy. However, when I use trigonometry, I understand that and I can solve the practice problems. Seeing a force diagram and using trig with to solve for the forces makes sense since I am a visual person. What I do not understand about vectors is the fact that although I can add and subtract them, I cannot find some the angles. When I try the vector method, I always only find one angle and the other angles I cannot solve.
-> My resolution: I am going to go to physics during lunch and work on vectors (and possibly practice using the force tables).
With F=ma, I like it a lot. I like doing math in physics so it's not a big challenge.
The actual challenges that I have are doing lab work/experiments and trying to derive conclusions from our data. I am not a handy person, so running experiments are always difficult because I make many errors. Also, during whiteboard discussions, when the class has to come to some sort of conclusion with the data, I have a hard time drawing that conclusion. I can find the answers when I am guided with help, but trying to come up with the equation/connection/pattern myself, that is very difficult.
-> My resolution: I will pay closer attention to detail, whether that be during labs or during the whiteboard discussion. I think that if I am more careful and attentive, I'll be able to make less errors and I'll have an easier time drawing those equations, connections or patterns.
Comments
Post a Comment