speed: a measure of how fast something is moving. The rate at which distance is covered (m/s)
velocity: speed in a given direction (m/s)
a=Δv/Δt so only a if there is a v
A baseball is thrown vertically in the air so that it returns to the ground exactly from where it was thrown. At what point during its motion does the baseball experience the lowest acceleration?
The acceleration due to gravity is a constant 9.8m/s2downward (assuming it’s on the surface of the Earth) throughout the baseball’s journey. It’s velocity is ever changing but the acceleration is constant.
A baseball is thrown vertically in the air so that it returns to the ground exactly from where it was thrown. At what point during its motion does the baseball have the lowest speed (ignore air resistance)?
At the highest point of its motion
An astronaut simultaneously drops a piece of paper and a pen from the same height above the surface of the moon. Which hits the ground first?
The acceleration due to gravity on the moon experienced by both the pen and the piece of paper is exactly the same and therefore they will reach the ground at exactly the same moment. If you tried this on Earth, the pen would most likely hit the ground first, but this is a result of greater air resistance experienced by the piece of paper not by a difference in the acceleration due to gravity. On the moon there is no atmosphere and therefore no air resistance explaining why both pen and paper reach the ground at the same time.
Which of the following explains why the turns on a racecar track are banked curves (angled upward)?
To decrease the force of friction between the car and the track
bc if you look at the diagram the Fn will help out the Fc so that the friction is decrease bc the normal will help the centripetal
Projectile Motion- horizontal component of velocity
v cos θ
at max height the vertical component of the velocity is _____
A rock is thrown upward at 50 degrees with respect to the horizontal. As it rises, neglecting air drag, its horizontal component of velocity
only the vertical changes and a = -9.8 at all pts of trajectory
Projectile Motion at top of trajectory
vy = 0 at the top of the trajectory vx ≠ 0 at the top of the trajectory
a = -9.8m/s^2
if thrown from the ground w velocity v the velocity of obj just before impact will be ___
given r of curve
kg of car and v of the car find stat. coeff.
Ff = mgu
150 g ball swung horiz in a circle with the readius 1 m if the ball makes 5 revolustions in a sec what is the Fc
5rev= 1 sec
1rev =.2 sec
vt=2πr (find v)
a= v2/r (find a)
if given 2 T and asked about efficiency
when given a springs Li and Lf and asked to find the E
simple harmonic motion means
as the obj moves towards x=0 (minimum displacement, the force decreases and reaches zero. as the force reaches 0, so does the acceleration F=ma. however the obj will gain speed as it moves towards the equilibrium position. thus the speed is greatest at x=0; a=0
if a pipe open on both sides formula?
n= 1,2,3, (harmonic)
What is the formula for frequency of an open pipe?
f = nv/2L
Closed Pipe frequency formula
-odd integers only
-closed end always nodes
-open ends always antinodes
speed of a wave
frequency of a wave
Frequency and Period for a mass on a spring
f = (1/2π)√(k/m)
T = 2π√(m/k)
period on a pendulum
Pressure for static fluids equation
Buoyant Force (Formula)
The upward force acting on a submerged object that is equivalent to the weight of the fluid displaced by the object.
Fb = ρfluidVg = g x mdisplaced fluid (weight) V = volume of fluid displaced m = mass of the displaced fluid
For an object that is submerged, Fb is equal to the pressure difference between the pressure at the top of the object and bottom of the object multiplied by the area of the surface of the bottom or top (pg 80) Fb = ΔP x A
if 2 pistons with the radius and the F of one given
use pascal's F1/F2 = A1/A2
relates presure of 2 different vessels
and also tells you that the smaller the area the faster it is
pressure btw 2 places
P = ρgh so the deeper one
flow rate equation
Q=flow rate= AV=V/t
water leaves a hole v and Q (flow rate) given find diameter... equtions
water sprout shoots water upwards w h and cross sectional A given find Vol. of water each min. EQUATIONS
PEgain=KElost Q=Av =volume/t
Changing Pipe Diameters equation
make sure the change the D to r
if the length of a pipe qudruples and the r triples what happens to the flow rate?
for ideal liquids the flow rate is independent of pipe lengths
Av=Av so the speed will decrease by a factor of 9 but the flow rate is constant
longitudinal wave such as a sound wave is one in which the particles move ____ to the direction of motion
sound generally moves fastest in ___ and slowest in ____
waves are readily formed on a stretched spring such a s slinky
sound wave doesn't travel in a vaccum
loudness or intensity level given by
60dB to 20dB is how much greater
Io= 1×10-12 W/m2
so its 104 greater
Area of a sphere
A = 4 π r2
intensity = power / area
doppler effect for ___
light and sound
when the source emits light of a particular wavelength and moves towards you ____
frequency increases and the wavelength appears to decrease
as sound approaches you the pitch and wavelength
sound source moves away
frequency (pitch) decreases and wavel. ↑
____ are always attractive and ____ can be repulsive or attractive
- gravitational force
- electrical force
___ cannot conduct heat or electricity to an appreciable extent
k, coulombs constant
an object that acquires a + charge ___
has lost electrons
F= (kq1q2) / r2
electric Field equation
E= F / q [N/C]
E= V / d [V/m]
E = (kq) / r2
The electric field is what kind of quantity?
E strngth within a metal is ___
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