Work Flashcards
Work: formula and SI unit
W: F * s (joule)
S: t * v.
Power: formula and SI unit
Rate of doing work/duration of work.
P = W/t. Watt or P = F * v.
Energy: SI unit
Joule
Kinetic energy
Ekin = 1/2 * m * v2
Gravitational potential energy
Epot = m * g * h
Elastic potential energy
Eelastic = 1/2 k * s2
Conservation of energy
The total amount of energy in an isolated system remains constant.
Ekin + Epot + Eelastic = constant.
Mass-energy equivalence
Every object with a mass (m) has a so-called rest energy E:
E = m * c2
C= speed of light.
Work done in force of friction.
‘ the sled moves at a constant velocity’
The acceleration is zero;
The net force acting on it is zero;
The force of friction is therefore equal to the pulling force = 30 N.
A boy with his sled (30kg) arrives at the bottomn of the slope with a velocity of 4 m/s. As he slows down on the horizontal section, he slides 24m before he stops.
A) calculate the work done by the force of friction that stops the movement of the sled.
As it’s deacceleration, the breaking force equals the kinetic energy but with a negative sign:
- 240 J.
Force of friction
Ff = W/s W= Ff * s
Work needed to lift blood.
Gravitational potential energy:
Epot : m * g * h Joule.
Final velocity
V= square root of 2E/m
Rest energy of electron in eV
E = m * c2
eV = 1.6 * 10 -19
Number gotten/eV= eV
Kinetic energy?
Elastic potential energy?
Gravitational potential energy?
Ekin: 1/2 * m * v2
Eelastic: 1/2 * k * s2
Epot: m * g * h
