DYNAMICS - FORCES

Objectives

Describe the effect of balanced and unbalanced forces on a body

Describe the ways in which a force may change the motion of a body

The Great Scientist Sir Issac Newton

4 January 1643 – 31 March 1727

Born in England and educated at Trinity College, Cambridge

Known as physicist, mathematician, astronomer, alchemist, inventor and philosopher

The Great Scientist Sir Issac Newton

Wrote the Philosophiae Naturalis Principia Mathematica in which he defined the 3 Laws of Motion in 1687

Dynamics

Kinematics deals with the motion of the body without looking at what causes the motion of the body (displacement, velocity and acceleration)

In dynamics, we look at what causes motion.

DynamicsAround Us

Can you name some examples where you can observe the work of dynamics?

Dynamics - Forces

What is force? A push or pull that one object exerts on

another which produces, or tends to produce motion, stops or tends to stop motion.

Vector (Remember how to represent a vector?)

Examples of Forces

Weight Contact Force

Tension Expansion Forces

Upthrust Resistance

Friction Centripetal Force

Magnetic Force Electrostatic Force

Dynamics - Balanced vs Unbalanced Forces

Balanced vs Unbalanced forces Book not moving Moving book Is there a net force acting on the train when when it is

moving at constant speed? Conclusion

Balanced Force Fnet = 0 No acceleration Unbalanced Force Fnet 0 Acceleration Acceleration in direction of net force (for linear motion

only)

Dynamics - Effect of Force on Motion

Go to http://www.rlgreene.org/Illuminations/html/Dynamics/

Demos/NewtonMotion1a.html Observe how the motion of the body changes with the

application of force in a different direction

Dynamics - Effect of Force on Motion

Body moves in different ways depending on how force is applied. Velocity and net force in same direction

Velocity increases in magnitude in original direction Velocity and net force in opposite direction

Velocity decreases to zero, turns around and increases in magnitude in direction of acceleration.

Velocity and net force at an angle Non-linear motion If the speed is constant, is acceleration zero?