Mechanics Flashcards
Equation linking s, u, t & a
S = ut + 1/2at²
Gravitational mass vs inertial mass
Both have the same numerical value; only difference is definition & method
Gravitational mass definition
A quantity that determines the gravitational force on the object
Inertial mass definition
A quantity that determines the acceleration of the object
Equation linking v, u, a & t
V = u + at
Equation linking s, v t & a
S = vt- 1/2at²
Equation linking v, u, a & s
V² = u² + 2as
Equation linking s u v & t
S = 1/2(u + v)t
Acceleration definition & equation
Rate of change of velocity
A = (v-u)/t
What is s?
Displacement
Horizontal & vertical motion what remains constant?
Horizontal = constant velocity(negligible air resistance)
Vertical = constant acceleration (-g)
Equation for range (horizontal displacement) of projectile
R or s = vcosθt
Weight (N) equation
Mass x gravitational field strength
Work done unit
Nm (same as joules)
Graphical method for determining work done
Area under force x distance graph
Power
Work done per unit time
Efficiency equation
Useful work out ➗ total energy in
Newton’s first law
- When no external forces act on a body (net force=0) the body will either remain at rest (v=0 ms-1) or continue to move with constant speed.
Newton’s second law
The rate of change of momentum is directly proportional to the unbalanced force acting on that body and takes place in the same direction
Impulse
Change in momentum (mv-mu)
Unit of momentum
Ns (same as kgms^-1)
Finding the impulse
Graphically: area under the curve of a force/time graph
Change in momentum = force X change in time
Perfectly elastic collision
One in which there is no loss of kinetic energy in the collision
principle of conservation of momentum
the total momentum of a system is constant provided external force does not act
why does drag force increase with speed?
objects encounter more fluid per second and hit it harder
velocity of x relative to y
subtract the velocity of y from x
size of buoyancy force
weight of fluid displaced
condition for a body to be in translational equilibrium
No external force acting on the body
what does dynamic friction do
opposes the relative motion between two touching surfaces
what does static friction do
STOPS the relative motion between two touching surfaces
gravitational field strength exam definition
the force per unit mass experienced by a small point mass placed in the field
