Forces Flashcards
How to tell if forces in equilibrium from question
Static/at rest
On the point of slipping/ limiting equilibrium
Constant speed
what does it mean if forces in equilibrium
forces are balanced
Left = right
Up=down
What does it mean if vector forces in equilibrium
F1+ F2+ F3 + …. = 0
If not in equilibrium what is taking place and how to resolve
Acceleration / deceleration
Resolve using F=ma where F is the resultant force
Friction rules
Always opposes the direction of motion
If static Fr<= uR
If in limiting equilibrium Fr= uR
where 0<=u
Objects motion when mgsinø> Fr max
Object will move down slope
Objects motion when mgsinø<=Fr max
Object will remain at rest
How to resolve force at an angle
Find the horizontaland vertical magnitudes of it (Fcosø and Fsinø)
Which way does tension act
pull object toghether. tension acts awa from the object and to the other tension
Feel like it pulls
What is Thrust
acts towards object and away from other thrust force (pushes)
Forces acting on whole system of a lift with 2 boxes in
Tension action up
(Mass if 2 boxes and lift)g acting down
There are 2 boxes stacked on top of each other what forces do these experience
Box A: mg acting down and R acting up
Box B: mg acting down R acting down (equal and opposite to R in A) N acting up which is the floor pushing on B
There are 2 boxes in a lift what forces does the lift experience
T acting up
Lg(weight of lift) acting down
N (Box B pushing in floor) acting down
Method of for connected particles
1) F=ma
2) F=ma
3) Simultaneous equations (usually find acceleration or tension)
4) SUVAT find v (which will then act as u when string breaks or particle hits floor)
5) Find new acceleration as T=0 when breaks or hits floor
6) More SUVAT, use new a, and u will be v from before
Uniform meaning
Weight acts at the centre
