Answer:
Q = 2.95*10^5 kJ
Explanation:
In order to calculate the energy required to melt the cooper, you first calculate the energy required to reach the boiling temperature. You use the following formula:
(1)
m: mass of cooper = 540 kg
c: specific heat of cooper = 390 J/kg°C
Tb: boiling temperature of cooper = 1080°C
T1: initial temperature of cooper = 20°C
You replace the values of the parameters in the equation (1):

Next, you calculate the energy required to melt the cooper by using the following formula:
(2)
Lf: melting constant of cooper = 134000J/kg

Finally, the total amount of energy required to melt the cooper from a temperature of 20°C is the sum of Q1 and Q2:

The total energy required is 2.95*10^5 kJ
The far right.
Fg is gravity which always acts down and since we assume the floor is flat the normal, Fn, acts opposite gravity, so straight up.
But you’re probably wondering about the pushing force, Fp, and the friction force, Ff. For the Fp, consider where the applied force is coming from. The head of the broom is on the floor and the man’s arms, where he’s applying the force from, is above and to the left, so when the man pushes the broom the force is down and to the right. The broom my not be moving down, but the applied force is still in that direction. And Ff always acts against motion so since the broom moves to the right, the friction is to the left.
The total mechanical energy of the notebook is <u><em>19J</em></u>.
Mechanical energy is the sum of potential energy and kinetic energy. It has no kinetic energy, because it's not moving. So its potential energy is all the mechanical energy it has.
(a) 154.5 N
Let's divide the motion of the sprinter in two parts:
- In the first part, he starts with velocity u = 0 and accelerates with constant acceleration
for a total time
During this part of the motion, he covers a distance equal to
, until he finally reaches a velocity of
. We can use the following suvat equation:

which reduces to
(1)
since u = 0.
- In the second part, he continues with constant speed
, covering a distance of
in a time
. This part of the motion is a uniform motion, so we can use the equation
(2)
We also know that the total time is 10.0 s, so

Therefore substituting into the 2nd equation

From eq.(1) we find
(3)
And substituting into (2)

Solving for t,

So from (3) we find the acceleration in the first phase:
And so the average force exerted on the sprinter is

b) 14.5 m/s
The speed of the sprinter remains constant during the last 55 m of motion, so we can just use the suvat equation

where we have
u = 0
is the acceleration
is the time of the first part
Solving the equation,
