Answer:
-58.8 J
Explanation:
The work done by a force is given by:

where
F is the magnitude of the force
d is the displacement of the object
is the angle between the direction of the force and the displacement.
In this problem, we are asked to find the work done by gravity, so we must calculate the magnitude of the force of gravity first, which is equal to the weight of the object:

The displacement of the object is d = 3.00 m, while
, because the displacement is upward, while the force of gravity is downward; therefore, the work done by gravity is

And the work done is negative, because it is done against the motion of the object.
Answer:
The weight of Earth's atmosphere exert is 
Explanation:
Given that,
Average pressure 
Radius of earth 
Pressure :
Pressure is equal to the force upon area.
We need to calculate the weight of earth's atmosphere
Using formula of pressure


Where, P = pressure
A = area
Put the value into the formula


Hence, The weight of Earth's atmosphere exert is 
To help you I need to assume a wavelength and then calculate the momentum.
The momentum equation for photons is:
p = h / λ , this is the division of Plank's constant by the wavelength.
Assuming λ = 656 nm = 656 * 10 ^ - 9 m, which is the wavelength calcuated in a previous problem, you get:
p = (6.63 * 10 ^-34 ) / (656 * 10 ^ -9) kg * m/s
p = 1.01067 * 10^ - 27 kg*m/s which must be rounded to three significant figures.
With that, p = 1.01 * 10 ^ -27 kg*m/s
The answers are rounded to only 2 significan figures, so our number rounded to 2 significan figures is 1.0 * 10 ^ - 27 kg*m/s
So, assuming the wavelength λ = 656 nm, the answer is the first option: 1.0*10^-27 kg*m/s.
Answer:
Explanation:
Expression for escape velocity
ve = 
ve² R / 2 = GM
M is mass of the planet , R is radius of the planet .
At distance r >> R , potential energy of object
= 
Since the object is at rest at that point , kinetic energy will be zero .
Total mechanical energy =
+ 0 = 
Putting the value of GM = ve² R / 2
Total mechanical energy = ve² Rm / 2 r
This mechanical energy will be conserved while falling down on the earth due to law of conservation of mechanical energy . So at surface of the earth , total mechanical energy
= ve² Rm / 2 r
Answer: His average speed in mph over the last 400 m is 7.7 m/s.
Explanation:
Given: Hicham El Guerrouj of Morocco holds the world record in the 1500 m running race. He ran the final 400 m in a time of 51.9 s.
We know that , speed = 
Here , distance = 400m and time = 51.9 s
Then, speed = 
Hence, his average speed in mph over the last 400 m is 7.7 m/s.