Kinetic Energy and Work

Question 1

Energy

Answer 1

Scalar quantity associated with the state of one or more objects.

Question 2

Kinetic energy K

Answer 2

Energy associated with the STATE OF MOTION of an object. The faster the object moves, the greater is its kinetic energy. When the object is stationary, its kinetic energy is zero. K=1/2m(v^2)

Question 3

1 Joule

Answer 3

1 J = 1 kg * 1 m^2/s^2 = 1 N * 1 m

Question 4

Work W

Answer 4

Amount of energy transformed to/from the object.
To the object -> positive work
From the object -> negative work 
Scalar quantity measured in Joules 
Can be both negative and positive

Question 5

Work equation

Answer 5

W=F(x)d, = Fd*cos(alpha) or dot product between F and d as vectors!
d

Question 6

Net work

Answer 6

Sum of the individual forces when there is more than one acting on the particle

Question 7

Work–kinetic energy theorem

Answer 7

W = ΔK 
Work = Change in kinetic energy of particle 
ΔK = Final K - Initial K

Question 8

Work done by the gravitational force

Answer 8

W = F(g)dcos(alpha) = mgd*cos(alpha)

Question 9

Spring force (restoring force)

Answer 9

Force that is always opposite to the direction of displacement of a spring, because this force wants to restored the relaxed state of a spring.
F(s) = -k * d -> Hooke’s Law
d

Question 10

Work done by the spring force

Answer 10

W = 1/2k((xi^2)-(xf^2))

xi

Question 11

Power P

Answer 11

Time rate at which work is done on the object.
Average P = W/Δt
Instantaneous power ("chwilowa")

Question 12

1 Watt

Answer 12

1 W = 1 J/s

Question 13

Lifting and lowering objects

Answer 13

ΔK = W(a) + W(g)

W(a)

Question 14

Work done by a variable force

Answer 14

When the force depends on a position of an object then the Work is equal to the integral from xi to xf from F(x), similarly with more dimensions.
Work is equal to the area below the curve made by F(x) in the interval from xi to xf