Motion

ISCI 2002

Speed • Speed: change in distance over time

• Speed = d / t

• Constant vs. Average Speed

• Speed is a ‘scalar’ quantity – No directional properties

Velocity • Velocity: includes the speed of an object plus direction.

• Velocity = d / t + direction!

• Displacement – Object moves from one location to another – Distance and direction from a starting point

Displacement

Velocity and Displacement are Vectors • Vectors: have both magnitude and a direction – Velocity, acceleration, displacement, etc.

• Vectors are represented by arrows

Vector Summation• Parallel vectors may be summed

• When vectors are at right angles– (a) Parallelogram Rules – (b) use trigonometry rules to solve

• Pythagorean Theorem

Vector Addition

Paralleogram Law • The so-called parallelogram law gives the rule for vector

addition of two or more vectors. For two vectors and , the vector sum is obtained by placing them head to tail and drawing the vector from the free tail to the free head.

Vector Resultant

Acceleration • Acceleration: is a change in the velocity of an object.

• Acceleration = v / t

• When you change directions, slow down, speed up, turn you are undergoing acceleration.

• Acceleration may be (+) or (-)

Instantaneous Speed and Velocity • Speed or velocity at any given moment in time – Speedometer in your car

Motion and Graphs

• Graphs– Straight-line or linear slope indicates a direct or

proportional relationship between the variables • Speed or velocity at that specific time

–Non - proportional • Slope of the line tangent to the curve of the line• Positive or Negative relationship between variables

Graphical Slopes • Slope: rise/run

• Change in position (y) over time (x)

Calculating the Slope of a Graph

Distance-Time Graphs

Constant velocity (+10 m/s); No acceleration

Changing, positive velocity – acceleration (change in velocity)

Constant Velocity – No Acceleration

Velocity – Time Graphs

Zero Acceleration

Constant Velocity – Zero Acceleration

Velocity-Time Graphs (Acceleration)