Download Goal #2 – Motion and Forces

Goal 2 – Motion and Forces
Displacement – the distance and direction between an object’s starting position and its current position.
Speed – distance travelled over time.
Velocity – speed and direction.
Average velocity (speed) – change in position over change in time.
Acceleration – the increase or decrease in velocity of an object over time.
Force – push or pull on an object
Net force – sum of all forces acting on an object.
Weight – the affect of the force of gravity acting on an object.
Acceleration due to gravity – the increase in speed of an object as it falls freely.
Displacement can be measured in meters (SI unit). Time is measured in seconds (SI unit).
A graph of distance (displacement) vs. time can show the velocity of an object. Divide distance by time. Velocity is measured in
meters/second (SI unit).
Objects that are travelling at a constant speed are said to have uniform velocity. (They are not speeding up or slowing down.)
Acceleration can be found by plotting a graph of velocity vs. time. The slope of the line is found by dividing the change in velocity by
the change in time. Acceleration is measured in meters/second/second (SI unit).
Newton’s Laws
(1st Law) Most objects have a tendency to continue their current pattern of motion unless an unbalanced force is applied to the object.
This is called inertia.
A force can be applied to help change an object’s motion. This force must be unbalanced for the object’s motion to be changed. Force is
measured in kgm/s/s, or in Newtons (N).
(2nd Law) The acceleration of an object is equal to the ratio of the net force over the mass of the object.
If the net force on the object is zero, then all the forces are balanced, and the object will not change its motion.
(3rd Law) When one object exerts a force on another object, the second object exerts an equal but opposite force on the first object.
(Action-reaction)
As an object falls freely, if we ignore air resistance, it will accelerate at a speed of 9.8 m/s/s.
The momentum of an object in motion is equal to the product of the object’s mass and its velocity.
Objects that aren’t moving have no momentum.
When two objects collide, momentum is conserved (initial momentum = final momentum)