Answer:
door handles are kept near the door handles that are in the door
H = 2.80t^3
h = 2.80 (1.55)^3 = 10.43
10.43 = 1/2 gt^2
10.43 x 2/9.8 = t^2
t = √2.12
= 1.45
Hope this helps
I am only a HS Freshman so I might be wrong
Answer:
3. Its potential energy and the formula for PE = mgh so you would use the weight given (Weight = mg) and mg is in the (Potential Energy) forumula so we multiply 3 by 30 and get 90 Joules
4. We would do the same thing with this: PE = mgh; PE = 10*3 = 30 Joules
Once again I am only a Freshman and I have taken Private AP Physics classes so just maybe wait for someone who is more confident.
This is just what I would answer
btw, for problem 5, the fromula for kinetic energy is 1/2*m*v^2
Answer:

Explanation:
The energy of a photon is given by:

where
is the Planck constant
is the speed of light
is the wavelenght of the photon
For the microwave photons in this problem,

so their energy is

Answer:
D
Explanation:
this is simple, because when air is removed, means that there is no particles in the jar so vacuum is achieved, and when you can't hear a sound means that the sound couldn't travel through the vacuum. which means that sound cannot travel through vacuum,
as a result, sound requires a medium ( air) travel from one point to another.
hope it helps, if not please report it so that someone else gets to try it