Forces Flashcards
What is the difference between a scalar and a vector
Scalars only have magnitude whereas vectors have both magnitude and direction
Names some scalars
Distance, speed, time, temperature, mass, density, energy, volume, charge,
Name some vectors
Displacement, velocity, weight, forces, acceleration, momentum
What is newtons 1st law
An object will remain at rest or continue moving with constant velocity if there is no resultant force acting upon it
What is newtons 2nd law
When an object experiences a resultant force its motion will change by either speeding up (accelerating) slow down (decelerating) or changing direction.
What is newtons 3rd law
Every action has an equal but opposite reaction. So if one object exerts a force on another object, the second object will exert an equal but opposite reaction force in the first object
What is the difference between a contact and non contact force
For contact forces the objects are physically touching whereas for non contact forces they are not
Give some examples of contact forces
Friction, air resistance, tension, normal contact forces
Give some examples of non contact forces
Gravitational forces, electrostatic and magnetic forces
What is weight
Weight is a non contact force acting on an object because of gravity. It depends on the gravitational field that it is in and the mass of the object.
What is the “centre of mass” of an object
The weight of an object may be considered to act at a single point referred to as the object’s “centre of mass”
What is the difference between mass and weight
Mass is the amount of matter in an object measured by a balance. Weight is the force acting on the object due to its mass and the gravitational field it is in, measured by a spring balance
what is a resultant force
a single force that can represent all the forces acting on an object
if two forces are in the same direction how do you calculate the resultant force
add them together
if two forces are in opposite direction how do you calculate the resultant force
take the smaller one from the bigger
name a force that is always down
weight
name a force that is always in the opposite direction to motion
friction, drag or air resistance
how do you calculate the resultant force when two forces are at right angles to each other
use Pythagoras theorem a² + b² = c²
what is word done the same as
energy transferred in moving something
how do you calculate work done
force x distance
what happens to the kinetic energy when work is done
it is turned into thermal energy or gravitational energy
what kind of force is work normally done against
either frictional or gravitational
what unit is the same as a newton meter
the joule
what does the term “elastic deformation” mean
that an object will change shape when a force is applied and then go back to its original shape when the applied force is removed
what does “inelastic deformation” mean
that an object will change shape when a force is applied and will not return to its original shape when an applied force is removed
what equation links force, extension and spring constant
F = Ke where F- force, k-spring constant, e-extension
can F=ke be used for compression or extension
both e- would be the compression of the spring or the extension
if a spring has not gone past its elastic limit what would a force, extension graph look like
a straight line through the origin, with a positive gradient (linear)
what happens if a spring goes past its elastic limit
it no longer returns to its original shape and is permanently deformed
how could you tell from a force extension graph if the spring had past its elastic limit
the graph would not be completely straight ( nonlinear)
rearrange E = 0.5ke² to make e the subject
e²= F/0.5k
