topic 8 - forces and energy

Question 1

what happens to energy when a system changes

Answer 1

energy is transferred and some energy is dissipated

Question 2

how can a system be changed

Answer 2

by forces doing work, electrical equipment doing work or. heating

Question 3

what is work done

Answer 3

energy transferred when a force moves an object through a distance

Question 4

work done =

Answer 4

force x distance

Question 5

change in gravitational potential energy =

Answer 5

mass x GFS x change in vertical height

Question 6

kinetic energy =

Answer 6

0.5 x mass x velocity^2

Question 7

how to reduce friction between objects’ surfaces when they move

Answer 7

lubrication

Question 8

efficiency =

Answer 8

useful energy transferred / total energy supplied

Question 9

what is power

Answer 9

rate of energy transfer

Question 10

power =

Answer 10

work done / time

Question 11

energy transferred is equal to

Answer 11

work done

Question 12

one watt is equal to

Answer 12

one joule per second

Question 13

what is contact force

Answer 13

when two object have to be touching for a force to act

Question 14

what is a non contact force

Answer 14

if two objects do not need to be touching for the force to act

Question 15

moment of a force =

Answer 15

force x distance normal to the direction of the force

Question 16

what is the principal of moments

Answer 16

the sum of clockwise moments = the sum of anti clockwise moments