Linear Motion
What is the expression for average velocity?
change in position/ change in time
In an air-free chamber, a pebble is thrown horizontally, and at the same instant a second pebble is dropped from the same height. Compare the times of fall of the two pebbles
they hit at the same time
You are trying to cross a river that flows toward the south with a strong current. You start out in your boat on the east bank desiring to reach the west bank directly west from your starting point. You should head your boat_________
in the general northwesterly direction
Which would hit the ground first if dropped from the same height in a vacuum, a feather or a metal bolt?
same time
this is an object's tendency to keep doing what it's doing (to maintain its state of motion); dependent on mass
inertia
In addition to displacement, which of the following must be used for a more complete description of the average velocity of an object?
time
For general projectile motion with no air resistance, the horizontal component of a projectile's acceleration ______
is always zero
True or False The magnitude of the resultant of two vectors cannot be less than the magnitude of either of those two vectors.
false
_____ is an example of a contact force, and _____ is an example of a field force
friction; gravity
How does the acceleration of an object change in relation to its mass?
Acceleration is
rate of change of velocity
For general projectile motion with no air resistance, the horizontal component of a projectile's velocity _____
remains a nonzero constant
a vector is a quantity that has _____ and _______
magnitude and direction
compared to its weight on earth, a 10 kg object on the moon will weigh ____
less
The law of inertia states that an object
in motion stays in motion in a straight line at a constant speed and an object at rest stays at rest unless acted upon by an outside force
when velocity is positive and acceleration is negative, what happens to the object's motion?
slowing down
The baseball catcher throws a ball vertically upward and catches it in the same spot as it returns to the mitt. At what point in the ball’s path does it experience zero velocity and nonzero acceleration at the same time?
at the top of its trajectory
why is weight considered a scalar quantity even though it is technically a force measurement?
we don't say we weigh 50 N downward, we just say 50 N, no direction just magnitude
A 10-N force and a 30-N force act in the same direction on an object. What is the net force on the object?
40 N
A jumbo jet cruises at a constant velocity when the total thrust of the engines on the jet is 40,000 N. How much air resistance acts on the jet?
40,000 N
___ are the units for velocity, ____ are the units for acceleration
m/s; m/s2
the horizontal component of a projectile's motion is ________ of the vertical component
independent
how is a scalar quantity different than a vector quantity?
magnitude but no direction
pressure is defined as _____/______
force/area
more surface area= less pressure
less surface area= more pressure
If the net force on an object is doubled, the acceleration of the object will
double assuming mass stays constant