Kinematics Flashcards
The big five
d = 1/2(vo + vf)t
vf = vo + at
d = vot + 1/2at2
d = vft - 1/2at2
vf2 = vo2 + 2ad
Free Fall Projectile:
equation for distance/discplacement (x), velocity (vx), and acceleration (ax).
x = voxt
vx = vox
vox = vocos(theta)
ax = 0
Free Fall Projectile Motion
Give the equation for distance traveled in y direction (y), velocity in y direction (vy), and acceleration (ay)
y = voyt + 1/2(-g)t2
vy = voy + (-g)t
voy = vosin(theta)
vy = 0 at peak
ay = -g
*Note that some are the same as the big five
Equation for velocity, acceleration, and force
v = ∆x/t
a = ∆v/t
F = ma = m∆v/t
If acceleration is constant, what equation can you use to find average velocity?
va = (vf - vi) / 2
If velocity is constant, then acceleration is ___
0
If velocity is constant, then net force is ____
0 (because acceleration is 0)
What is Newton’s first law?
F = ma
object at rest will stay at rest and object in motion will stay in motion unless acted upon by another (unbalanced) force.
therefore, Fnet = 0 when v is constant
What is Newton’s second law?
∑F = sum of all the forces in all directions = F1 + F2 + F3 +…
An object experiencing a net force will experience an acceleration in that direction.
What is Newton’s third law?
F1 on 2 = F2 on 1
FA = - FB
every action has an equal and opposite reaction
Analyzing the equation F = ma
1) If Fnet is constant and you decrease the mass by half, how will this affect acceleration?
2) If the mass stays constant, and the Fnet doubles, how will this affect acceleration?
1) a will double in value
F = ma ⇒ m = F/a ⇒ 2m = F/a ⇒m = (1/2)F/a aka m = F/2a
2) a will double because Fnet and a are directly proportional
How do you find the net force in the x and y direction?
Fnet,x = _______
Fnet,y = _______
Fnet,x = max = macos(theta)
Fnet,y = may = masin(theta)
Equation to find the force of gravity on an object?
F = mg
*Note this is equal to the weight of the object
Equation for force of static and kinetic friction
Ff,s ≤ µsFN
Ff,k = µkFN
On an inclined plane, how do you find the Fg and the FN?
Fg = mg
FN = mgcos(theta)
Is it possible for a car to have the same velocities but different speeds?
No
Distinguish between velocity and speed
velocity is the change in discplacement over time
speed is the total distance traveled over time
Will someone’s velocity always be the same numerical value as their speed?
No
If a person runs around a track and stops where they started, their discplacement will be zero, which means their velocity will be zero; however, their average speed will actually have a numerical value
acceleration is how fast an object’s ____ changes over time
velocity
Can an object be accelerating even if it’s speed is constant?
Yes, because velocity is not speed. velocity is discplacement over time. So an object can have a consistent speed but be changing direction, which means acceleration is also changing.
If the acceleration vector is parallel and in the same direction (or has the same sign) as the velocity vector, the object’s speed is _____
increasing
(direction remains constant)
If the acceleration vector is in the opposite direction or has the opposite sign of the velocity vector, the object’s speed is ____
decreasing
(direction remains constant)
If the acceleration vector is perpendicular to the velocity vector, this means that the object’s speed is ____ and that it’s direction is _____
speed is constant
direction is changing
If the acceleration vector has an angle 0-90 or 90-180 compared to the velocity vector, what does this say about the object’s speed and direction?
speed is either increasing or decreasing (same direction or sign is increasing, opposite direction or sign is decreasing)
direction is changing