Physics—Forces
(True/False) If an object has unbalanced forces acting on it, it's net force will be equal to zero.
False. For an object with unbalanced forces acting on it, net force ≠ 0.
True. Energy is the ability to do work.
(True/False) A sound wave is a longitudinal wave.
(True/False) In a sound wave, the vibration of the medium is parallel to the direction that the wave is traveling in.
True. A sound wave is a longitudinal wave.
True. In a sound wave (longitudinal wave), the vibration of the medium is parallel to the direction that the wave is traveling in.
Generally speaking, how do we see things?
The reason we see things is that light reflects off of them and enters our eyes. Our eyes then detect the light and send signals to the brain, which forms an image in our mind.
Answer the following (both teams can get this, but you must get everything right). What is
acceleration due to gravity (m/s2)? Kinetic energy equation? Potential energy equation? Wave speed equation? Free fall equation (i.e. dropping a ball off a bridge)?
acceleration due to gravity (a) = 9.8m/s2
KE = 1/2 x m x v2
PE = m x g x h
v = λ x f
d = 1/2 x a x t2
What is the acceleration due to gravity (a) in m/s2?
Acceleration due to gravity (a) = 9.8m/s2
A certain blue whale weighs 136,000 kg (~300,000 lbs), and is moving at a speed of .5 m/s. What is the kinetic energy of the blue whale?
Hint* 1 N = kgxm/s2
KE = 1/2 x m x v2
KE = 34,000 Nxm
Draw a transverse wave and label the following parts: crest, trough, wavelength, amplitude.
Also, for a transverse wave, what direction does the medium vibrate relative to the direction the wave travels.
Draw.
In a transverse wave, the medium vibrates at right angles (or, perpendicular) to the direction the wave travels.
What is polarized light? Why would this be beneficial?
Polarized light is light waves that vibrate in only one plane (usually in the horizontal plane). This can be helpful when wearing polarized lenses in sunglasses. it can help people see and not be blinded by the sun.
Yes, because the force he is exerting on the box (upward force) is in the same direction as the motion of the box (up).
True. Static friction is greater than kinetic friction. You experience this when you try to move something heavy, and when it gets easier to push/pull once it gets moving.
(True/False) Speed and kinetic energy are inversely proportional. In other words, when one goes up the other goes down, and vice versa.
False. Speed and kinetic energy are proportional to one another.
KE = 1/2 x m x v2
Why is there no sound in space?
Space lacks a medium (air) through which sound waves may travel.
Draw light refracting through a converging lens. (Hint* converging lenses have a convex shape)
(I will judge the drawing(s))
The sides of a converging lens are curved outward (toward the middle)
The sides of a diverging lens are curved inward (toward the middle)
What is the relationship between pitch, sound, and frequency?
(I will judge the answer(s))
Pitch is an indication of how high or low a sound is, which is primarily determined by the frequency of the sound wave.
Sound waves with low pitch have low frequency.
Sound waves with high pitch have high frequency.
(True/False) I sit on a desk and it does not break and I do not fall through it. This is because for every action force (my force on the desk) there is a reaction force (the desk puts a force on me).
True. And if the desk does not break or bounce me off of it, then that means the force of the desk on me is balanced (equal to) the force of me on the desk.
An object resting on top of a table falls off of the table and onto the ground, It loses its __________ energy.
PE = m x g x h
One end of a rope is vibrated to produce a wave with a wavelength of 1.5 meters. The frequency of the wave is 3.0 hertz. What is the speed of the wave in m/s?
v = λ x f
v = 1.5 m x 3.0 1/s
v = 4.5 m/s
What kinds of lens does the human eye have?
The human eye has a converging lens.
What is the Doppler effect?
A change in sound frequency caused by the motion of the sound source, motion of the listener, or both.
A boy throws a rock off of a bridge, and it takes 3 seconds for it to hit the ground. How many meters high is the bridge above the ground?
Use d = 1/2 x a x t2
distance (meters, m) = 44.1 meters
A man lifts a box up. Then, he starts walking down the hall while still holding the box up. Is the man doing work on the box?
No. No work is done by the man on the box because, even though he is still putting a force on the box, it is not in the direction of motion.
(True/False) Generally, men's voices are lower in frequency than women's voices.
True. Men have a lower pitch than women, and therefore the sound waves of their voices have lower frequencies.
Where is light focused onto in the human eye, and what kinds of conditions can a poor focusing of this light lead to?
The light is focused by a converging lens onto the retina. In nearsightedness (myopia) the light is focused in front of the retina, not on the retina. In farsightedness (hyperopia) the light is focused behind the retina,, not on the retina.
What is the greenhouse effect and how does it relate to global warming?
(I will judge the answer(s))
The greenhouse effect is the process by which certain gases (principally water vapor, carbon dioxide, and methane) trap heat that radiates from earth.
If there is an excess in the amount of these gases, then the earth's atmosphere will get warmer.