physics: simple machines, circular motion

vector

directed physical quantity

vector examples

force, velocity, displacement, acceleration

scalar

undirected physical quantity

scalar examples

temperature, mass, energy, distance

inertia(trägheit)

an object stays in a state of rest unless a force is acting upon it

gravity

the force of attraction between masses

definition of work

force in direction of motion times distance (displacement)

power

the work done in a specific time

energy

the ability to do work

block and tackle

a lifting mechanism which consists of ropes and pulleys

lever

a rod mounted to rotate around an axis

examples of levers from daily life

scissors, nutcracker, door handles, seesaw

movement of the force (torque)

a force acting on a lever exerts a torque (movement of the force), creating a turning effect. The rod will start to rotate.

lever arm

distance between axis of rotation and the point of application of the force

examples of a uniform circular motion

earth rotates around the sun, microwave, hands of a clock

period

the time required for a complete revolution

frequency

number of revolutions per time unit

angular speed

angles covered in radians per time unit

centripetal acceleration

change of direction in the velocity

centripetal force

the center-seeking force that pulls an object towards the center of a circle, keeping it on a circular path rather than flying off in a straight line

What is the condition for a ball to continue in a circular path *and not fall down) in the upmost point, if it is whirled around on a string in a vertical circle? Or: what is the condition for a roller coaster to not fall down in the upmost point of a looping?

v≥√gr​ (speed at top must be at least √gr so centripetal force ≥ weight).