Chapter 5

Question 1

Work

Answer 1

• Equal to the product of the magnitudes of the displacement and the component of the force parallel to that displacement
• Force but no displacement= no work
• SI: Joule (J)
• Scalar quantity

Question 2

When is work positive?

Answer 2

• The force (or component) is in the direction of motion (and displacement)
• Ex: pushing a box

Question 3

When is work negative?

Answer 3

• The force (or component) is opposite to the direction of motion (and displacement)
• Ex: catching a ball

Question 4

Kinetic Energy

Answer 4

• The energy of motion
  
  • when an object is moving with a constant acceleration due to an applied force
  • Net force causes object to accelerate, changing velocity
• SI: J
• Scalar quantity

Question 5

Work-Kinetic Energy Theorem

Answer 5

-The net work done by all the forces acting on an object is equal to the change in the object’s kinetic energy

Question 6

Potential Energy

Answer 6

• (U or PE) The energy associated with an object because of the position, shape, or condition of the object
• Released into kinetic energy
• Types: Gravitational and Elastic

Question 7

Gravitational Potential Energy

Answer 7

• (Ug or Pg)The potential energy stored in the gravitational fields of interacting bodies
• SI: J
• Greater potential with greater height, less potential with less height

Question 8

Elastic Potential Energy

Answer 8

-(Ue or Pe) The energy available for use when a deformed elastic object returns to its original configuration

Question 9

Hooke’s Law

Answer 9

-When in equilibrium ( a mass is hanging at rest)< we can say the ideal spring force is F(s)= k(delta X or delta y)

Question 10

Conservation of Energy

Answer 10

-The total energy of an isolated system is always conserved

Question 10

Non conservative Force

Answer 10

• If work done by it in moving an object, it does depend on the objects path
• Ex: Friction

Question 11

Conservative Force

Answer 11

• Work is done by moving an object and is independent of the objects path
• Work done by it in an object through a round trip=0
• Ex: Gravity

Question 12

Power

Answer 12

• The rate at which work is done
• Inversely proportional to time
• Directly proportional to work

Question 13

Efficiency (Mechanical Efficiency)

Answer 13

• Unitless (joules cancel out)

- Less than 100%

Question 14

Total Mechanical Energy

Answer 14

-The sum of all kinetic energy and all forms of potential energy

Question 15

Horsepower

Answer 15

-1 horsepower= 750 watts