I would say that work is being done in all the situations because technically in physics work is done whenever force is applied through a distance.
Answer:

Explanation:
Given that,
Heat required, Q = 8000 J
Mass, m = 400 g
The change in temperature, 
The heat required due to change in temperature is given by :

So, the specific heat of the substance is 
Answer:
<u>Atom</u><u> </u><u>is </u><u>particle</u><u> </u><u>of </u><u>matter</u><u> </u><u>that </u><u>uniquely</u><u> </u><u>defines</u><u> </u><u>a</u><u> </u><u>chemical</u><u> </u><u>element</u><u>.</u>
Examples of atom:
- Hydrogen [ H]
- Neon [Ne]
- Argon [A]
- Iron [Fe]
- Calcium [Ca]
<h3>
About Atom:</h3>
Atom consists of a central nucleus that is usually surrounded by one or more electrons .Each electron is negatively charged. The nucleus is positively charged and contains one or more relatively heavy particles known as protons and neutrons.
An early model of the atom was developed by the physicist Ernest Rutherford in 1913. He was the first to suggest that atoms are like miniature solar systems except that the attractive force is not caused by gravity, but by opposing electrical charged.
Hope this helps....
Good luck on your assignment...
Answer:
The rocket has to be launched 8 m from the hoop
Explanation:
Let's analyze this problem, the rocket is on a car that moves horizontally, so the rocket also has the same speed as the car; The initial horizontal rocket speed is (v₀ₓ = 3.0 m/s).
On the other hand, when starting the engines we have a vertical force, which creates an acceleration in the vertical axis, let's use Newton's second law to find this vertical acceleration
F -W = m a
a = (F-mg) / m
a = F/m -g
a = 7.0/0.500 - 9.8
a = 4.2 m/s²
We see that we have a positive acceleration and that is what we are going to use in the parabolic motion equations
Let's look for the time it takes for the rocket to reach the height (y = 15m) of the hoop, when the rocket fires its initial vertical velocity is zero (I'm going = 0)
y =
t + ½ a t²
y = 0 + ½ a t²
t = √ 2y/a
t = √( 2 15 / 4.2)
t = 2.67 s
This time is also the one that takes in the horizontal movement, let's calculate how far it travels
x = v₀ₓ t
x = 3 2.67
x = 8 m
The rocket has to be launched 8 m from the hoop
Without air resistance, both balls reach the ground at the same instant.
Neither horizontal motion nor weight affects vertical motion.