The distance you free-fall from rest is D = (1/2) (g) (T²) <== memorize this
Height of the platform = (1/2) (9.8 m/s²) (2.4 sec)²
Height = (4.9 m/s²) (5.76 s²)
Height = (4.9/5.76) meters
Height = 28.2 meters (a VERY high platform ... about 93 ft off the water !)
Without air-resistance, your horizontal speed doesn't change. It's constant. Traveling 3.1 m/s for 2.4 sec, you cover (3.1 m/s x 2/4 s) = 7.4 m horizontally.
12.00 min = 0.2 hr
8.00 min = 0.15 hr
Total distance:
(10.0 km/hr) (0.2 hr) + (15.0 km/hr) (0.15 hr) + (20.0 km/hr) (0.2 hr)
= 8.25 km
Average speed:
(10.0 km/hr + 15.0 km/hr + 20.0 km/hr) / 3
= 15 km/hr
Change in position:
(10.0 km/hr) (0.2 hr) + (15.0 km/hr) (0.15 hr) - (20.0 km/hr) (0.2 hr)
= 0.25 km
Average velocity:
(10.0 km/hr + 15.0 km/hr - 20.0 km/hr) / 3
≈ 1.67 m/s
Force = (mass) x (acceleration)
= (0.75 kg) x (25 m/s²)
= (0.75 x 25) kg-m/s²
= 18.75 newtons .
Note that even though we're talking about a 'hit', the acceleration only
lasts as long as the bat is in contact with the ball. Once the ball leaves
the bat, it travels at whatever speed it had at the instant when they parted.
Any change in its speed or direction after that is the result of gravity, air
resistance, and the fielder's mitt. I learned a lot about these things a few
weeks ago, since I live in Chicago, about 6 miles from Wrigley Field, in
a house full of Cubs fans.
<span>1. They’re invisible - RADIO WAVES
2. They have colors. - VISIBLE LIGHT WAVES
3. They’re used to learn about dust and gas clouds. - BOTH
4. They can travel in a vacuum. </span> - BOTH<span>
5. They’re used to find the temperature of stars. </span>- VISIBLE LIGHT WAVES<span>
6. They have energy. </span> - BOTH
Answer:
Roughly three quarters of the Sun's mass consists of hydrogen (~73%); the rest is mostly helium (~25%), with much smaller quantities of heavier elements, including oxygen, carbon, neon, and iron. The Sun is a G-type main-sequence star (G2V) based on its spectral class.
Explanation:
