Physics Exam II

Question 1

since force is a vector, what does it have?

Answer 1

magnitude and direction

Question 2

what is the net force

Answer 2

the combination of all of the forces and the resulting motion

Question 3

normal force

Answer 3

when an object rests or pushes on a surface, the surface exerts a push on it that is directed perpendicular to the surface

Question 4

friction force

Answer 4

in addition the normal force, a surface may exert a frictional force on an object, directed parallel to the surface

Question 5

tension force

Answer 5

a pulling force exerted on an object by a rope, cord, etc…

Question 6

weight

Answer 6

the pull of gravity on an object down

Question 7

Newton’s Second Law

Answer 7

If a net external force acts on an object, the object accelerates. The net external force is equal to the product of the object’s mass and the object’s acceleration.

1. a net force in a certain direction causes acceleration in that direction
2. the magnitude of acceleration caused by the net force depends on the object’s mass (think F = ma)
3. only external forces acting on an object affect that object’s acceleration (internal forces have equal and opposite that cancel)

Question 8

What happens to acceleration if you double the net external force?

Answer 8

it doubles

Question 9

what happens if you apply the same net force to an object with double the mass

Answer 9

the acceleration is 1/2’ed

Question 10

what are the units of N

Answer 10

1kgm/s2

Question 11

is gravity dependent on mass? is weight dependent on things?

Answer 11

gravity is not; weight depends on mass and gravity

Question 12

if you have 2 different objects with different masses, what is the acceleration vs force?

Answer 12

a = the same for both
f = different

Question 13

inertia - which law is it associated with

Answer 13

• the tendency of an object to resist change in motion
• mass dependent (harder to move bigger things)
• newton’s first law

Question 14

newton’s first law

Answer 14

an object at rest tends to stay at rest and an object in uniform motion tends to stay in motion with the same speed and in the same direction unless acted upon by a net force

Question 15

when is an object in equilibrium

Answer 15

when the net external force on it is zero

Question 16

a book is lying at rest on a table. the book will remain there at rest because ?

Answer 16

there is no net force acting on it

Question 17

a hockey puck slides on ice at constant velocity? what is the net force acting on the puck?

Answer 17

zero

Question 18

newton’s third law

Answer 18

if object A exerts a force on object B, object B exerts a force on object A that has the same magnitude but is in the opposite direction; these 2 forces act on different objects
- force pair
- action and reaction

Question 19

friction

Answer 19

a force that resists the sliding of one object past another

Question 20

static friction

Answer 20

if you push or pull on an object to make it slide but it doesn’t move, we call it the force that is preventing sliding

Question 21

kinetic friction

Answer 21

if the object is sliding we call the force that opposes this motion a …

Question 22

rolling friction

Answer 22

force always acts opposite to the motion of a rolling object whether it’s rolling uphill, downhill, or on a horizontal surface

Question 23

fluid resistance

Answer 23

resistance experienced by an object when it moves through fluid

Question 24

drag force

Answer 24

force that resists the motion of an object through liquid such as water or gas such as air

F = cv2

Question 25

centripetal force equation

Answer 25

sum F = mv2/r