Forces Flashcards
Contact force
the force acting when two interacting object have physical contact with each other
EXAMPLES
- frictional force
- applied force
- normal contact force
- elastic force
- viscous force
Non contact force
the force acting over a distance without physical contact between two interacting object
EXAMPLE
- gravitational force
- magnetic force
- electric force
Effects of force
- start a motion
- stops a motion
- change the speed of the motion
- change the direction of motion
- changing the shape
- changing the size
- turining an object
- exerting pressure on surfaces
Measurement of force
- force is measured in newtons
- meausured by extension spring balance or compression spring balance
Normal contact force
- equal magnitude as the weight
- acts in the opposite direction of weight
Why is a (book) stationary - normal contact force
the normal contact force on the book acts perpendicularly to the surface of contact between the book and the table. It prevents the book from falling to the ground because of its weight
Frictional force
Friction is the contact force that acts between two surfaces in contact with each other that opposes or tends to oppose or resist motion. it usually acts opposite to the direction of motion at the point of contact
Viscous Force
- air resistance or water resistence
- friction depends on the surface but air resistance depends on the speed and surface area
Gravitational force
- otherwise known as weight
w = mg
Mass
- the measure of the amount of substance ina body
- scalar
- kg
- measure by beam balance
- does not vary
- does not depend on gravitational field strength
Weight
- gravitational force exerted by earth on a body placed on earth
- vector
- newtons
- varies
- calibrated spring balance
- depends on the gravitational field strength
electric force
- exists between charges
magnetic force
- ## force exerted by a magnet or a magnetic material
Newton’s first law of motion
- a body will remain in its state of rest or uniform motion in a straight line unless acted upon by a resultant force
inertia deifintion
- refers to the reluctance of a body to reluct a change in the state of rest or motion of the body
Comparison question
- A is more massive
- a more massive body has a greater reluctance to reluct changes in motion
Table question
all masses have inertia. all the objects have inertia and are initially at rest.hence when the objects are subjected to a sudden force , they will tend to stay at rest.
Large vehicles
- have greater inertia, more difficult to stop the motion of the vehicle
Balanced forces
when there are two forces of equal magnitude acting on the object in opposite direction,they cancel out each other, and there is a net force of zero and no change in motion.
Unbalanced forces
- if the forces acting on the object do not cancel out each other, there is a rsultant force and a net force of not zero, causing a change in motion.
Forces acting on object
- when two forces are acting on the object in the same dircetion, the net force is the sum of the two forces( they share the same line of action)
- when two unequal forces are acting on the same object but in different direction, the net force is the difference between the forces.
Pressure
Pressure = force/ area
Amount of force acting perpendicularly on a unit area
Atmospheric pressure
- air moloecules around us move with high velocity
- when they collide with surfaces, they exert a force
- the pressure exerted by air in the earth’s atmosphere on objects exposed to air
Straw theory
- when the straw is sucked, the air pressure in the straw decreases
- the atmospheric pressure acting on the water is larger than the air pressure in straw.
- a net force is exerted on the surface which causes the fluid to enter the straw
Balloon theory
as the balloon rises into the air, the atmospheric pressure acting on the balloon from the outside is smaller than the air pressure inside.
- there is a net fore that pushes on the balloon from inside causing it to expand.
squash theory
the blood in our body exerts a larger pressure than the air. hence there is a net force acting from insdie our body, preventig from benig squashed
