Equations relating to mass, weight, density and forces and motion
Density = Mass
Where Density (kgm-3)
Volume
Mass (kg)
Volume (m3)
Weight = Mass x
Gravitational Field Strength (9.81) Weight (N)
Mass (kg)
Gravitational Field Strength (Nkg-1)
Resultant Force = Mass x Acceleration Resultant Force
(N)
Mass (kg)
Acceleration (ms-2)
Forces
Balanced forces do not alter the velocity of a body. When forces
are balanced an object will continue in a state of uniform motion.
Definitions
Mass
is the property of a body which resists change in motion
Note the GCSE definition: Mass is
the amount of matter a body contains is no longer satisfactory.
Weight is the force on an object due to gravity acting on its mass.
A Newton is the force which when applied to a mass of 1 kg produces an acceleration of 1 ms-2.
Connected Particles Questions using F=ma
Example: A 750kg car is pulling a 200Kg trailer. The Engine force = 12000N. Calculate the acceleration and tension.
T
12000
200 750
Note how the tension force is equal is size but opposite in direction between the car and the trailer
From this diagram it is possible to construct two simultaneous equations on describing the motion of the car the other of the trailer.
12000 – T = 750a (1)
T = 200a (2)
(1) + (2) 12000 = 950a
a = 12.63
When a = 12.63 ms-2
T = 2526.3 N