MAE 242: DYNAMICS. Instructor Dr. Samir N. Shoukry Professor, MAE & CEE. assistants K. Mc Bride Dhananjy Rao Dony Oomen. http://cw.prenhall.com/hibbeler/medialib/studypak/index.html Login Name: htkau Password: y2k3. Key to a grade of A in MAE242.
Instructor Dr. Samir N. ShoukryProfessor, MAE & CEE
assistants K. Mc BrideDhananjy RaoDony Oomen
Login Name: htkau Password: y2k3
Kinematics is the science of characterizing motion
Kinetics looks into the forces that cause the motion
Position is defined by a vector that originates from an origin. The vector is called POSITION VECTOR.
The origin may be selected at any convenient point.
Example: Your average speed from Morgantown to New York was 70 miles/hour. On your way you took a speeding ticket for speeding at a velocity of 92.5 miles/hour.
So, What is Velocity?
Change in time
While your average speed on the trip was 70 MPH, your speed varied from 5 MPH driving out of your garage, to 92.5 MPH when you where caught speeding at mile post 36 on I68.
Velocity is an instantaneous vector that describes the rate of change in position with respect to time.
Velocity is a VECTOR quantity
Velocity = v
OPosition, Speed, and Velocity
A particle moves from P to P’ in Δt seconds
Δr is the change in position vector r in Δt seconds
The magnitude v of the VECTOR v is the speed of the particle. Since Δr=PP’, as t0 the distance PP’ Δs. Thus, the average speed:
The VELOCITY VECTOR is always TANGENT to the path
Change in time
dtAcceleration and Deceleration
We enter I79 at speed of 45 MPH. Since the allowed speed limit is 70 MPH; one increases the velocity of his car. While a Cadillac can accelerate to 79 MPH in 6 seconds a Subaru reaches the same velocity in 15 seconds. Driving at 85 MPH, a police car spotted; the driver reduce his speed to 65 MPH in 16 seconds. He was spotted speeding at 82 MPH.
Acceleration is a vector that describes the rate of change in velocity with respect to time.
Acceleration is a VECTOR quantity
Total distance=7+(7-(-25))-(-25-(-18))=46 ft