# Physical Science Chapter 5

version from 2015-09-17 00:46

## Section

Question Answer
forcea push or pull or any action that involves the interaction of objects and has the ability to change motion.
strong nuclear forcethe force that holds the nucleus of an atom together. this force is very strong but only reaches a very short distance.
electromagentic forcethis force acts between positive and negative charges. this force golds atoms together in molecules.
weak forcethis force causes some kinds of radioactivity
gravitythis force causes all masses to attract to each other. your weight comes from the mass of earth attracting the mass of your body
what are the four Elementary Forces?strong nuclear force, gravity, weak force, electromagnetic force
pound (lb) the metric unit of force, it is equal to 4.448 N { for smaller amounts we use the ounce (oz) 1 pound= 16 oz }
newton(N)the metric unit of force, it is equal to the force needed to make a 1 kg object accelerate at 1 m/s^2
1 kg of mass has a weight of ___.9.8 N of force.
to predict the effect of the force, you need to know both its ____.strength and direction. (strength is usually measured in units).
What are the two ways that objects affect each other through forces?contact forces and "at-a-distance" forces
list 5 contact forcesfriction, normal force, gravity, air resistance, tension
list 3 at a distance forcesgravity, magnetism, and electricity
ropes are used to ___. springs are used to ___.transfer forces or change their direction. make and control forces
the force created by a spring is proportional to the ratio of the extended or compressed length _____. divided by the original (resting) length.
tensiona pulling force tat acts in rope, string, or other object
extensiona "stretch" or decrease in size
weightthe force of gravity on an object
massthe amount of matter in an object
matteranything that has mass and takes up space.
weight is a force that depends on ____.mass and gravity
gravity exerts a force of ____ on every kilogram of mass.9.8 N
weight=m (mass in kg) x g (strength of gravity N/kg)
frictiona force that resists motion
friction is a ___ force.contact
what can be used to reduce friction?lubricants, magnetic levitation, ball bearings
sliding fricrtionthe friction force that resists the motion of an object moving across a surface
static frictionthe friction force that resists motion between two surfaces that are not moving, keeping the object at rest.
net forcethe sum of all forces acting on an object
net force can be _______.zero (balanced) or non zero (unbalanced).
balanced forcescombined forces that result in a zero net force on an object
equilibriumthe state in which the net force on an object is zero. equilibrium does not mean that there are no forces acting on it,
normal forcethe perpendicular force that a surface exerts on an object that is pressing on it.
free-body diagramsa diagram showing all the forces acting on an object