Answer:b
Explanation: If you look at the line on the graph, you can see that it is going downward, meaning it has a negative slope, and choice b is the only one that has a negative slope
Answer:
#2) The spaceship's forward motion must be slowed down so the earth's gravitational pull on it will be stronger than the ship's forward motion.
Heat, like sound, is kinetic energy. Molecules at higher temperatures heave more energy, thus they can vibrate faster. Since the molecules vibrate faster, sound waves can travel more quickly.
So the answer is A.
-- The speed of light in air is very close to 3 x 10⁸ m/s.
Whatever the actual number is, it's equivalent to roughly
7 times around the Earth in 1 second. So for this kind of
problem, you can assume that we see things at the same time
that they happen; don't bother worrying about how long it takes
for the light to reach you.
-- For sound, it's a different story. Sound in air only travels at
about 340 m/s. It takes sound almost 5 seconds to go 1 mile.
-- Now, the lightning and thunder happen at the same time.
The light travels to you at the speed of light, so you see the
lightning pretty much when it happens. But the sound of the
thunder comes poking along at 340 m/s, and arrives AFTER
the sight of the lightning.
The length of time between the sight and the sound is about
99.9999% the result of the time it takes the sound to reach you.
If the thunder arrived at you 3 seconds after the light did, then
the sound traveled
(340 m/s) x (3 s) = 1,020 meters .
(about 0.63 of a mile)
(If you're worried about ignoring the time it takes
for the light to reach you ...
It takes light 0.0000034 second to cover the same 1,020 meters,
so including it in the calculation would not change the answer.)
Answer is 6 tires.
This is a projectile question.
First make sure units are consistent - express speed in m/s.
20 km/h = 20000m / 3600 s = 5.56 m/s
Assume the takeoff point of the ramp is at ground level (height, h, = 0m). We need to determine how long Joe is in the air, and use that time to calculate the horizontal distance he traveled.
Joe is traveling 5.56 m/s on a ramp angled at 20 degrees. There are vertical and horizontal components to his speed:
Vertical speed = 5.56sin20 = 1.90 m/s
Horizontal speed = 5.56cos20 = 5.22 m/s
An easy way to proceed is to calculate the time it takes for Joe’s vertical speed to reach 0m/s - this represents the time when Joe is at his maximum height and is therefore halfway through the trip. Double whatever time this is to find the total time of the trip. Remember he is decelerating due to gravity:
Time to peak:
a = Δv / Δt
-9.8 = -1.9 / Δt
Δt = 0.19s
Total trip time:
0.19 x 2 = 0.38s
Now that we have the total tome Joe is in the air, we can find the horizontal distance he traveled:
v = d / t
5.22 = d / 0.38
d = 1.98m
Now divide this total distance by the length of an individual tire to find the number of tires he will clear:
1.98 / 0.3 = 6.6 tires
Therefore he can jump 6 tires safely (he will land in the middle of the 7th tire).
Lots of steps I know but just try to think of the situation and keep track of the vertical and horizontal things!
