Chapter 6 worksheet - Work & Kinetic Energy PDF

Preview

Summary

Work & Kinetic Energy...

Description

LARC Physics 7C Tutorial

Jack Yu [email protected] Work & Kinetic Energy

Learning Goal Students will be able to: • Correctly calculate Work based on Force & Displacement (both are vectors) • Apply work-energy theorem and explain its coexistence with conservation of energy.

Chapter 6 Lecture Review & Questions (10 min) W=

if F is constant

dW = ______ds

if F is a function of s (of course, if F is constant, this equation is still true, but more complex than need be)

=>

W=∫

𝑑𝑠

Kinetic Energy:

Work-energy theorem:

LARC Physics 7C Tutorial

Jack Yu [email protected]

Guided Practice (10 min) How to apply Work-Energy Theorem? Is the Mechanical Energy of the book conserved?

A 1.50-kg book is sliding along a rough horizontal surface. At point A it is moving at 3.21 m/s, and at point B it has slowed to 1.25 m/s. (a) How much work was done on the book between A and B?

(b) If -0.750 J of work is done on the book from B to C, how fast is it moving at point C?

Solution: https://www.slader.com/discussion/question/a-150-kg-book-is-sliding-along-a-roughhorizontal-surface-at-point-a-it-is-moving-at-321-ms-and-at-p/

LARC Physics 7C Tutorial

Jack Yu [email protected]

Guided Practice: student-student (15 min) Think: can we safely use Conservation of Energy here? And why?

Two blocks are connected by a very light string passing over a massless and frictionless pulley Traveling at constant speed, the 20.0-N block moves 75.0 cm to the right and the 12.0-N block moves 75.0 cm downward. How much work is done

(a) on the 12.0-N block by (i)

gravity and (ii) the tension in the string?

(b) How much work is done on the 20.0-N block by (i) gravity (ii) friction, and (iii) the normal force?

(c) Find the total work done on each block.

Solution: https://www.numerade.com/questions/two-blocks-are-connected-by-a-very-light-stringpassing-over-a-massless-and-frictionless-pulley-text/

LARC Physics 7C Tutorial

Jack Yu [email protected]

Independent practice (10 min) How can we express Work?

Suppose the coefficient of kinetic friction is a function of displacement s: μ = 3-s (the friction vary from one position to another) A person pushes the box to slide to the right from A to B non-stop. How much work have the pushing force done to the box?...