physicis chapter 4
a car travels east at constant velocity the net force on the car is
zero
an action/ reaction pair of forces
act on two different objects
a force of 1N is
1kg*m/s^2
equal forces act on isolated bodies, A and B, the mass of B is 3x the mass of A, the magnitude of acceleration of A is
3x that of B
a woman is straining to lift a large crate, but without success because it is too heavy. how are the magnitudes of the forces related while the person tries unsuccessfully to lift the crate (P is upward force, C is vertical constant force, W is the weight)
P+C=W
newtons first law
an object in motion will continue in motion at a constant velocity unless acted on by a net external force
a steel beam hangs from a cable as a crane lifts the beam, what forces act on the beam
gravity and tension in the cable
the term mass refers to the same physical concept as
inertia
the mass of a body
is independent of the acceleration due to gravity
You stand on a spring scale on the floor of an elevator. Of the following, the scale shows the highest reading when the elevator:
moves upward with increasing speed or moves downward with decreasing speed
a circus performer of weight W is walking along a high wire, the tension in the wire is
much more that W
acceleration is always in the direction
of the net force
the inertia of a body tends to cause the body to
resist any change in its motion
newtons second law
the acceleration of an object is proportional to the net force on it and inversely proportional to its mass
magnitude of the acceleration of an object the least
the magnitude of forces in opposite direction
magnitude of the acceleration of an object the greatest
the magnitude of forces in the same direction
in general any surface exerts two forces on objects that are in constant with it, one force is parallel to the surface and the other is perpendicular to the surface, what are these forces called
the parallel force is friction force and the perpendicular force is the normal force
using a rope an object is lowered at a steady decreasing speed
the rope tension is greater than the objects weight
a feather and a lead ball are dropped from rest in vacuum on the moon, the acceleration of the feather is
the same as the lead ball
a 1500kg car travels a straight track at 60mph, a skier speeds up as she skies downhill, which is the net force greater
the skier
if you are standing on the floor motionless what are the forces that act on you
weight force and normal force
mass differs from weight in that:
weight is a force and mass is not
if you are not wearing a seat belt and the car you are driving hits a fixed barrier you will hit the steering wheel with some force, this is because
you continue moving even after the car has stopped
