Module 3 - Section 2 - Forces In Action Flashcards
What is needed in order for an object to start or stop moving or accelerate or decelerate ?
A net ( resultant ) force is needed for an object to accelerate and all of the above - there is a net force when the forms acting on a body are not balanced
When is there a net force ?
There is a net force when the forces acting on an object are not balanced
What happens if the forces acting on an object are balanced ?
IF the forces acting on an object are balanced then the object is in equilibrium
For example a cat would be inn equilibrium if the reaction forces would equal the weight of the cat
Does acceleration just mean a change in speed?
Acceleration could mean a change in speed or direction or both
What do free-body force diagrams show ?
Free-body force diagrams show all forces on a single body
So not the forces it exerts on the rest of the world - just the forces that are acting on the body
What’s the best way to work out if there is a net force on a body
Best way is to draw a free-body force diagram
What should you remember when drawing free body diagrams ?
Forces are vector quantitates therefore you have to draw the magnitude and the direction of the force
What are some examples of common forces acting on an object ?
Weight - acting directly downwards
normal contact force - if an object exerts a force on a surface, the surface exerts an equal and opposite force
tension - if a string is pulled tight - tension is the force pulling equally on the objects at either end of the string
Friction - IF an object is moving, it usually has a friction force acting on it in the opposite direction to motion
What is acceleration proportional to ?
Acceleration is proportional to force
What’s the equation for net force ( resultant force )
And what does it mean ?
Net force = mass x acceleration
The more force you have acting on certain mass, the more acceleration you have
It says that for a given force the more mass you have, the less acceleration you get as if you have the same amount of net force and then you just add lots of mass for e.g. a car if its going 20mph and then you add lots of mass to it then it will get slower and slower ( acceleration will be less )
What did Galileo say ?
He said that all object fall at the same rate ( if you ignore air resistance )
if you ignore air resistance, what happens if you drop a heavier and alight ball at the same time ?
They will both hit the ground at the exact same time because they both get accelerated by 9.81 - but you might think the heavier one will hit the ground first but no - because its heavier then in f=ma the mass will be bigger but the a will stay the same as its accelerated by gravity and the light one as well so the heavier ball will have a higher net force but the same acceleration as the light ball - the heavier ball will just do more impact once it lands for e.g. make a bigger hold in the floor if you dropped it in sand but it will still hit the sand at the same time.
