(a) The stone travels a vertical distance <em>y</em> of
<em>y</em> = (12.0 m/s) <em>t</em> + 1/2 <em>g t</em> ²
where <em>g</em> = 9.80 m/s² is the acceleration due to gravity. Note that this equation assume the downward direction to be positive, and that <em>y</em> = 0 corresponds to the height from which the stone is thrown.
So if it reaches the ground in <em>t</em> = 1.54 s, then the height of the building <em>y</em> is
<em>y</em> = (12.0 m/s) (1.54 s) + 1/2 (9.80 m/s²) (1.54 s)² ≈ 30.1 m
(b) The stone's (downward) velocity <em>v</em> at time <em>t </em>is
<em>v</em> = 12.0 m/s + <em>g t</em>
so that after <em>t</em> = 1.54 s, its velocity is
<em>v</em> = 12.0 m/s + (9.80 m/s²) (1.54 s) ≈ 27.1 m/s
(and of course, speed is the magnitude of velocity)
Answer:
B
Explanation:
for the motion every night, it is because the Earth spins on its axis.
for the changes over a year, this is because the Earth rotates around the sun.
for the changes over hundreds, thousands or millions of years, this is because the whole solar system (including the Earth, of course) rotates with all the other stars in our galaxy around the center of the galaxy. and each star system has its own orbit (similar to the planets in our solar system).
it is very rare to see objects outside of our galaxy without a telescope, but they change too over a long period of time, because our galaxy not only rotates by also moves through the universe, and these other objects move on their own too.
Answer:
Note that:
Particles in a:
gas are well separated with no regular arrangement.
liquid are close together with no regular arrangement.
solid are tightly packed, usually in a regular pattern.
Explanation:
Answer:
a) 2.5 m/s²
b) 6.12 m/s
Explanation:
Tension of rope = T = 356N
Weight of material = W = 478 N
Distance from the ground = s = 7.5 m
Acceleration due to gravity = g = 9.81 m/s²
Mass of material = m = 478/9.81 = 48.72
Final velocity before the bundle hits the ground = v
Initial velocity = u = 0
Acceleration experienced by the material when being lowered = a
a) W-T = ma
⇒478-356 = 48.72×a
⇒a = 2.5 m/s²
∴ Acceleration achieved by the material is 2.5 m/s²
b) v²-u² = 2as
⇒v²-0 = 2×2.5×7.5
⇒v² = 37.5
⇒v = 6.12 m/s
∴ Velocity of the material before hitting the ground is 6.12 m/s
Answer: 6s
Explanation:
Vs=32m/s speed at beginning of slowing down
Vf=0m/s stop speed
a= -6 m/s² acceleration
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Use equation for acceleration :
a=(Vf-Vs)/t
a*t=Vf-Vs
t=(Vf-Vs)/a
t=(0-36)/-6
t=-36/-6
t=6 s
