Physics Question...Please help...10 Points!!!?

Question

Comment Critically on the following claims:

(a) an object allways accelerates in the direction of the net force
(b)A lower net force is needed to accelerate an object from rest to 10m/s than is required to accelerate it from rest to 20m/s irrespective of the time take.


Best answer gets 10 Points!!!

Answer 1

a)an object allways accelerates in the direction of the net force
--- u dint tell us u had to do it as a well proven question or for basic understanding? never mind....if they ask u this in school then follow the explaination----
by newtons first law of motion,...(i'm assuming u know it)...'unless and untill a force acts on it' ---so a body would move if adequate force was applied(that overcame its friction and inertia)

as u know...forces cancel each other as well.
this happens according to the law of vectors.
thus if two forces are acting in different directions, then the resultant force is always in another direction depending on how they cancel each other and according to their magnitude which is the resultant direction.
so finally,...there be only one force left...with a particular direction and a particular magnitude....and now..applying newton's forst law of motion...it is proved that an object allways accelerates in the direction of the net force(newton's 2nd law states that force causes acceleration---u can also explain this by saying that,velocity changes hence acceleration occurs)


(b)A lower net force is needed to accelerate an object from rest to 10m/s than is required to accelerate it from rest to 20m/s irrespective of the time take.-----
the answer is NO.
we have to take the time into consideration. if we have to stop such a high speed in less time...then we have to apply a lot of force....remember---force causes acceleration..it causes a change per unit time...if u want more change per unit time...u have to apply more force
so thats it

Answer 2

a)Since (net F) = m*a is a vector equation with net F and a being vectors and m being scalar the 1 st condition holds true.

b) (net F)= m*a and v=at therefore (net F) =mv/t or Ft= mv.
As u see this equation involves time. Hence if one must acclerate a body to 10m/s in say 1 second and to 20m/s in 2 seconds then force required are the same. In case we have 5 seconds to accelerate the body then this case requires even lesser force than the former.

Answer 3

a) Not true in all situations. Net force can be applied to an object that is 1) Greater in mass than the kinetic energy imposed and will not move 2) Object is imposed by another object and cannot move. Without reference as to how much force is used and the mass of the object and direction, the statement is subject to too much speculation for a more accurate response.

b) Absolutely. It's why our newer satillites with Ion Drives attain their speeds. The force of the ionic reaction takes longer to move the objects mass and achieves greater speed than other conventional methods. That's of course, if time remains irrespective.

Answer 4

(a) is definitely true. An object always accelerates along the net force acting on it. It is different wheather the body moves in the direction of net force or not. The body may or may not move in the direction of net force, but the direction of net force is always along the direction of the net force. (the body must not be perfectly elastic)
(b) there is no relation between force and change in velocity. it is rather the impulse which is related to change in velocity. the relation is given by F*t (impulse) = m (v - u).
so you cannot ingore time while relating force with change in velocity.

Answer 5

The trick to both Q is that
F = ma

Force and a (acc) are directional quantities (vector) with components in coordinates of analysis...

F prop. to a

m is the proportionality constant,, and F is DIRECTLY proportional to a.
Therefore, greater F means more a,, to have greater a, u need more force.

Answer 6

Not enough ingormation. Also, whats the question?