If the sign of work is negative, that means the force and the motion are in opposite directions.
Let's say you see something roll off of the shelf. You catch it, and you let it down slowly and gently.
Gravity exerted down-force on it and it moved down. Gravity did positive work on it.
YOU exerted UP-force on it and it moved down. YOU did negative work on it.
(Also, the falling object exerted down-force on your hand, and your hand moved down. The falling object did positive work on your hand ! Where did THAT energy come from ? It came from the potential energy that the object had while it was on the shelf. Your hand absorbed that energy on the way down, doing negative work. So the object didn't have any kinetic energy when it reached the floor, and it did NOT splinter the floor or shatter in smithereens. It had barely enough energy left to make a sound when it hit the floor.)
Answer:
Explanation:
The intensity of an electromagnetic wave can be expressed in terms of the magnetic field using the next relationship:
(1)
- c is the speed of light (3*10⁸ m/s)
- μ₀ is the permeability of free space (in vacuum ) (1.26*10⁻⁶ N/A²)
- B₀ is the magnetic field
Now, let's define the relationship between power (P) and average intensity (I).
- P is the power
- A is the area crossed
So we can calculate the power.
Finally, energy is the product of P times time, so:
I hope it helps you!
Answer:
Explanation:
From work energy theorem
Work done by all forces = Change in kinetic energy
Lets take
m= mass of object
h=height from the ground surface
initial velocity of object = 0 m/s
The final velocity of object is v
Work done by gravitational force = m g . h
The final kinetic energy = 1/2 m v²
So
Work done by all forces = Change in kinetic energy
m g h = 1/2 m v² - 0
v² = 2 g h
Velocity
Because velocity is speed with direction. In this scenario, the speed has not changed, but the direction did.
Answer:
Masses and distance between them
Explanation:
The gravitational force between two objects can be calculated using Newton's Gravitational Law.
However, using logic, we can already dictate what the answer will be, for example. We know that the bigger an object is, the stronger its gravity is. This can be seen with how the moon is much smaller, and also has much less gravity.
Also, the distance between two objects also influences the gravity. This can be seen the further an object gets from Earth, the less of a pull the gravitational field has on it. Another example is that Pluto (being very far from the sun) has less of a gravitational effect from the sun, in comparison to Mercury (the closest plant to the sun).
