Speed Velocity Acceleration Freefall Describing Motion Speed Velocity Acceleration Freefall

Speed Instantaneous speed Average speed Distance moved per unit time Units ms-1 kph mph cms-1 distance moved time taken

Distance and speed are scalar quantities Scalar Quantity Magnitude Number and unit Always positive Follows arithmetic rules Vector Quantity Magnitude and direction May be positive or negative Does not follow arithmetic rules

Vector Quantities Displacement Velocity Distance + direction Displacement = final position – initial position Velocity Speed + direction Average velocity = displacement time taken

Question Are the magnitudes of speed and velocity Alwaysssss the same Sometimessssss the same Neverrrrrr the same?

More questions Page 34 Page 35, #s 1, 2 and 3

The velocity of a body is constant or zero if the forces are balanced. Newton’s First Law The velocity of a body is constant or zero if the forces are balanced.

Acceleration The rate of change in velocity Change in speed Speeding up Slowing down deceleration Change in direction Both Average Acceleration = change in velocity time taken

Questions, page 37

Graphs Displacement versus time Velocity versus time Slope of the graph = average velocity Velocity versus time Slope of the graph = average acceleration Area under the graph = distance traveled

Graphs

Example Who won the race? Who stopped for a rest? How long did he stop for? How long did Bob take to complete the race? Calculate Albert's average speed.

Interpreting graphs What is the greatest distance the object has traveled from its starting point? What is the average speed of the object for time intervals: 0 to 2 min 2 to 6 min 2 to 7 min 0 to 8 min Where is the object at the end of 8 min?

Speed and Acceleration Choose the correct words from the following list to describe the motion during each part of the journey accelerating decelerating steady speed stationary

Interpreting graphs What is the maximum velocity of the object? Determine its average acceleration between 0 and 10s 10 and 30s 10 and 40s 0 and 40s

Force and Acceleration Newton’s 2nd Law If an unbalanced force acts on the body, then the body accelerates Equation acceleration = force mass

The Physics of Falling

The Physics of Falling Terminal Velocity Freefall Motion where only gravity is acting on the body Acceleration due to gravity, g Air resistance is negligible Terminal Velocity The maximum speed of a falling object When upward forces balance downward forces on the object

The Physics of Skydiving

The End