5.1 - 5.4

Question 1

define ‘work’

Answer 1

the product of force and the distance moved in the direction of the force. measured in joules

Question 2

what are the common forms of energy

Answer 2

kinetic,
gravitational potential,
chemical,
thermal,
elastic potential,
electrical,
nuclear,
sound

Question 3

what is the principle of conservation of energy

Answer 3

energy can’t be created or destroyed only transferred from one form to another. the energy of a closed system remains constant

Question 4

what is kinetic energy

Answer 4

the energy due to the motion of an object with mass

Question 5

what is gravitational potential energy

Answer 5

the capacity for doing work as a result of an object’s position in a gravitational field

Question 6

how can you derive the equation for GPE

Answer 6

start with Work=forcedistance. to keep constant kinetic energy apply a force equal to the weight (mg). if an object is lifted by a height h then work=mgh. since the energy transferred is to GPE then GPE=mgh

Question 7

define power

Answer 7

the rate of energy transfer. measured in Watts

Question 8

how can you derive the equation Power=Force*velocity

Answer 8

start with Power=Work done/time. Work done= forcedistance therefore power=(fx)/t. distance/time = velocity therefore Power= Forcevelocity

Question 9

define ‘efficiency’

Answer 9

the ratio of useful output energy to total input energy. often expressed as a percentage