w6

Question 1

What is work

Answer 1

• Work is done when a force acting on some object moves it over a distance
  
  • Only the force parallel to the displacement does the worK

Question 2

Is work vector or scalar

Answer 2

Work is a scalar - no direction associated with it

Question 3

Unit for work

Answer 3

Joules

Question 4

Positive vs Negative work

Answer 4

• Positive work results from forces that try to speed up an object
• Negative work results from forces that try to slow down an object

Question 5

What is energy

Answer 5

• Energy is the ability to do work
• Energy is potential work.. not actual work

Question 6

Work vs Energy

Answer 6

• Energy can be stored
• Work is the result of releasing energy
  
  • Work is a measure of how much energy has been transferred

Question 7

What is the sum of KE and PE

Answer 7

Mechanical Energy

Question 8

Define Kinetic energy

Answer 8

Is energy of an object has because of its motion

Question 9

Define Grav PE

Answer 9

• When we do work against gravity i.e lifting something up, the work we do is stored
  
  • This is because object can do work on its way back down
• Energy stored by virtue of its position is called potential energy

Question 10

Conservative forces and key fact

Answer 10

• One for which the work done against it, doesnt depend on the path taken
  
  • Only conservative forces is where potential energy exists

Question 11

Examples of Conservative Forces

Answer 11

• Gravitational
• Elastic
• Electric
• Magnetic

Question 12

Non Conservative Forces and key fact

Answer 12

• The work which you do against friction, does depend on what path you take
• Work done against friction is not stored as PE

Question 13

Power definition and unit

Answer 13

• The rate at which work is done
  
  • Measured in Watts

Question 14

What is Momentum

Answer 14

Defined as an object’s inertia in motion

Question 15

Inertia vs Momentum

Answer 15

• Inertia of an object tells us how much that object resists being accelerated
  
  • All objects with mass have inertia
• Momentum of an object tells us how much momentum it has
  
  • Only moving objects have momentum

Question 16

What is an impulse

Answer 16

Force over a time-interval

Question 17

Define the conservation of Momentum

Answer 17

• The total momentum of two objects that collide is conserved
  
  • This only occurs in any closed system where no external forces act during the exchange of momentum

Question 18

What is a collision

Answer 18

A collision is defined as two objects striking one another, where the time of collision is short enough that external forces may be ignored

Question 19

Inelastic collision vs Elastic collisions

Answer 19

An inelastic collision is one where momentum is conserved but kinetic energy is not conserved
In elastic collisions both kinetic energy and momentum are conserved