P8: Forces Flashcards
what is a
scalar?
quantities that only have MAGNITUDE
what is a
vector?
have both MAGNITUDE and DIRECTION
WHAT IS
WEIGHT AND MASS?
weight: force acting on an object due to gravitational attraction.
MASS: amount of matter in object
weight equn?
w=mg
what is
resultant force? and what does it determine?
single force that describes all forces operating on an object
determines:
- direction of objects
- magnitude of force on object
work done equn?
w=fd
what is newton’s first law?
object remains at rest, or move with constant velocity unless acted upon by resultant force
what is newton’s second law?
the accelleration of object is proportional tp resultant force acting upon it and inversely proportional to object’s mass
what is newton’s third law?
every action, has an equal and opoosite reaction
acceleration eqn?
f=ma
what is inertia?
the tendency of an object to continue in its state of rest /at a constant speed unless acted upon by an external force
what is inertail mass? and equn?
property of an object that describes how difficult it is to change its velocity
inertial mass= force/acceleration
what is inertail mass? and equn?
property of an object that describes how difficult it is to change its velocity
inertial mass= force/acceleration
pressure in liquid equn?
pressure= height of column x density of liquid x gravitational field strength
what does size of upthrust depend on?
density of fluid
volume of fluid displaced
explain why a car has maximum speed?
- maximum forward force by motor
- as speed increases, air resistance increases
- until air resistance = forward force so car can no longer accelerate
why do objects sink?
- weight is greater than upthrust
- greater density than water
why does an object float?
weight is equal to upthrust
- density less than water
why does atmospheric pressure decrease as altitude increases?
- less molecules of air as altitude increases
- less force over an area
what is centre of mass?
point through which the weight of the object acts
explain the changing motion of a skydiver in terms of forces acting on a skydiver when falling?
- air resistance is lower than force of weight - ACCELERATES
- as acceleration increases, air resistance increases
- so weight/gravity = air resistance
- he reaches terminal velocity
why when jumping from higher altitudes , does the sky diver reach higher speed than if he jumped from lower altitude?
- high altitude means less dense air
- so air resistance on sky diver is less
- so can accelerate for longer before reaching terminal velocity
