Transcript ME101 Lecture 8 9

Kinetics of Particle
Lecture 8: Tuesday, 9/15/15
Today’s Objective
Kinetics of rectilinear motion
What is Kinetics?
• Kinetics is the study of the relations between
unbalanced forces and the resulting changes in
motion.
Solution Methods for kinetics problems:
• (A) direct application of Newton's second law (called the
force-mass-acceleration method),
• (B) use of work and energy principles, and
• (C) solution by impulse and momentum methods
What is Mechanics?
A. Application of Newton’s Second Law
Newton’s second law equation:
F = ma
Units
Equation of Motion
Types of problems:
• Unconstrained motion
• Constrained motion
• Rectilinear motion
• Curvilinear motion
Rectilinear Motion
• Motion along a straight line
Free Body and Inertia Body Diagrams
Problem 3/1 : The 50-kg crate is projected along the floor with
an initial speed of 7 m/s at x = 0. The coefficient of kinetic friction is
0.40. Calculate the time required for the crate to come to rest and the
corresponding distance x travelled.
Problem 3/35
Given: The nonlinear spring has a tensile force-deflection relationship given
by:
, where x is in meters and is in newtons. Determine the
acceleration of the 6-kg block if it is released from rest at x = 100 mm
Kinetics of Particle – Curvilinear Motion
Lecture 9: Thursday, 9/17/15
Today’s Objective
Kinetics of Curvilinear motion
Kinetics of a Particle
Curvilinear Motion:
1. Normal and Tangential (n-t) coordinates
Curvilinear Motion
Curvilinear Motion:
2. Polar (r, 𝜃) coordinates
Problem 3/50
The 4-oz slider has a speed v = 3 ft/s as it passes point A of the smooth guide,
which lies in a horizontal plane. Determine the magnitude R of the force which
the guide exerts on the slider.
a. Just before it passes point A of the guide
b. As it passes point B.
Problem 3/53
The hollow tube is pivoted about a horizontal axis through point O and is made
to rotate in the vertical plane with a constant ccw angular velocity of 3 rad/s.
If a 0.2 lb particle is sliding in the tube toward O with a velocity of 4 ft/s
relative to the tube when the 𝜃 = 300 is passed, calculate the normal force
exerted by the wall of the tube on the particle at this instant.