Work is done when a force is applied

Work is done when a force is applied along the direction of motion of an object. W = Fd( Cos q) • To have work, you need a force and a displacement, and they must be along the same axis. Work is not a vector ! The unit for work is the Newton meter • d d

+W = -F-d (Cos q )? - Work +d -F + Work -F -d -d -d -F + Work F

W = Fd (Cos q ) Force must be measured in same axis as the displacement y F 40 Fx x dx

How much work is needed to pull the box 10 meters? y N 0 5 = F 40 Fx D x=10 m x

How much work is needed to pull the box 10 meters? y W = Fx (Cos q ) Nm F= 50 N 40 x Fx x

Impulse Newton’s 2 nd Law rewritten Acceleration is the change in velocity divided by the time interval Multiply by the change in time F d Area= F x d =Work

Quantify the work done

5 Impulse W=_____ Newton ’s 2 nd Law rewritten Acceleration is the change in velocity divided by the time interval Multiply by the change in time. W=_____ 10 10 8

Impulse Newton’s 2 nd Law rewritten Acceleration is the change in velocity divided by the time interval Multiply by the change in time

Definition of Power Amount of work done per time period FYI …. . 1 hp = 746 Watts! Power also equals…

Read only Types of Energy Kinetic Energy All moving things! Potential Energy Electrical Gravitational Thermal, Spring Potential Nuclear Chemical

Energy vs Work Energy is the ability to do work, and work is the process of transferring energy Energy can be stored-work cannot W = Energy gained !!! Dy F

Kinetic Energy resulting from work causing motion kinetic energy Therefore, anything that is moving has both momentum (r) and kinetic energy (K) To calculate an object’s kinetic energy: U k= 2 1/2 mv

Graviational Potential energy (Ug) Potential energy is energy due to an object’s position. PE must be measured relative to some point where PE is defined to be zero. Upe = mgh “ Pete eats my green ham ”

Elastic potential energy (Uepe) When an elastic object is stretched or compressed, it stores energy. EPE = 1/2 kd 2 “EPE = 1/2 Katy squared” k = spring constant, a value that describes the strength or stiffness of an elastic material d = distance spring is stretched or compressed from its natural length

The spring in a dart gun converts spring energy into moving energy The KE from running is converted to Stored EPE in the pole which gives the Vaulter back vertical KE.

What is a k value man ? ? ?

Hooke’s Law : Frestore=-kx xi Dx xf Concerning elastic objects, we will find that force is proportional to stretch. The Slide general equation shown should indicates the slope (k) is the force per unit length of stretch. Fa = -Fr

K value is proportionality of Force to stretch

Using Hooke’s Law Slide. Calculate the spring constant k of the 3 spring Frestore=-kx

Work - Energy Theorem Energy is the ability to do work , so if work is done it is because energy was expended https: //www. youtube. com/watch? v=Mq. Gh 1 s. Tp. ZPg