Forces
acceleration
acceleration - the change in velocity over a certain amount of time
an object that slows down is decelerating
distance / time relationship
if an object moves along a straight line the distance travelled can be represented on a graph
the speed of an object can be calculated from the gradient of its distance / time graph
if an object is accelerating its speed can be determined by drawing a tangent and measuring the gradient
distance = y axis
time = x axis
the acceleration of an object can be calculated from the gradient of a velocity / time graph
velocity= y axis
time = x axis
an object falling through a fluid initially accelerates due to the force of gravity, eventually the resultant force will be zero and the object will move at its terminal velocity
Newton's 1st law
1st law - if the resultant force acting on an object is zero then the object is stationary or is moving at a constant speed
so the speed of an object will only change if a resultant force is acting upon it
inertia - the tendency of objects to continue in their state of rest or of uniform motion
Newton's 2nd law
the acceleration of an object is proportional to the resultant force acting on the object and inversely proportional to the mass of the object
inertial mass is a measure of how difficult it is to change the velocity of an object and is defined as the ratio of force over acceleration
Newton's 3rd law
whenever two forces interact the forces they exert on each other are equal and opposite