# Advice 1: How to find the fall time body

If you neglect air resistance, the time falling bodies does not depend on its mass. It is determined only by the height and acceleration due to gravity. If you reset with the same height two bodies of different mass fall at the same time they.
You will need
• calculator.
Instruction
1
The height from which the falling body, the SI units are meters. Acceleration of free fall given in the reference already transferred in units of this system are meters divided by seconds squared. To Land on the middle lane it is 9.81 m/s2. In terms of some of the tasks specified other planets, e.g. the Moon (1.62 m/s2), Mars (3,86 m/s2). When both reference values are given in SI units, the result will be in units of the same system - seconds. And if the condition specified body mass, ignore it. This information is superfluous, it can lead in order to check how well you know physics.
2
To calculate the time of falling body, multiply the height by two, divide by the acceleration of gravity, and then from the result, extract the square root:

t=√(2h/g) where t is time, s; h - height, m; g - acceleration of free fall, m/s2.
3
The task may require to find additional information about such things as what was the velocity of the body at the moment of touching the ground or at a certain height from it. In the General case the speed is calculated like this:

v=√(2g(h-y))

Introduced here the new variables: v - velocity, m/s and y is the height of where you want to know the speed of the falling body, m. it is Clear that h=y (i.e., at the initial moment of the fall) speed is zero and when y=0 (at the moment of touching the ground, before the stop of the body) the formula can be simplified:

v=√(2gh)

After the touch of the earth has already occurred and the body is stopped, the speed of his fall again equal to zero (of course, if it is not spryginia and not jumped again).
4
To reduce the force of impact after free fall parachutes are used. First drop in is free and takes place in accordance with the above equations. Then the parachute opens, and is a smooth deceleration due to air resistance, which now can not be neglected. The patterns described by the above equations no longer apply, and a further reduction in height is slow.

# Advice 2: How to find Mars

Mars is the fourth farthest the Sun and seventh in size of the planets of the Solar system. It got its name after the Roman God of war. Sometimes Mars is called the red planet, reddish tint of the surface gives the oxide of iron contained in the soil.
You will need
• Amateur telescope or powerful binoculars
Instruction
1
The opposition of Earth and Marsand
When the Earth is exactly between the Sun and Marsω, i.e. at a minimum distance equal to 55.75 million km, the ratio of the planets is called confrontation. At the same time he Mars is in the direction opposite the Sun. Such violence occur every 26 months at different points of the orbits of Earth and Mars. This is the most favorable points for observation of the red planet in Amateur telescopes. Once in 15-17 years, there are the great confrontation: the distance to Marsand the minimum, and the planet reaches its greatest angular size and brightness. The last great confrontation was 29 January 2010. The next one will be July 27, 2018.
2
The conditions of observation
In the presence of the Amateur telescope you should look for Mars in the sky in times of struggles. The surface detail available for observation only during those periods when the angular diameter of the planet reaches the maximum value. Large Amateur telescopes are available many interesting features on the planet's surface, seasonal evolution of the polar caps of Marsand the signs of Martian dust storms. In a small telescope you can see the "dark spots" on the surface of the planet. You can see the polar caps, but only during the great confrontations. A lot depends on experience, observations, and atmospheric conditions. So, the more observation experience, the less can be a telescope to "capture" Marsand parts of its surface. Lack of experience is not always kompensiruet expensive and powerful telescope.
3
Where to look
The evening and morning Mars is visible in the red-orange light, and in the middle of the night in yellow. In 2011, Mars can be seen in the sky during the summer and until the end of November. Until August planet can be seen in the constellation Gemini, in the Northern hemisphere of the sky. Since September, Mars is visible in the constellation of Cancer. It is located between the constellations of Leo and Gemini.
Note
If the experience of observation is small, should wait a period of confrontation.

# Advice 3: How to find force of air resistance

To determine the force of resistance of air create the conditions in which the body begins under the action of gravity to move uniformly. Calculate the value of gravity, it is equal to the force of air resistance. If the body moves in the air, picking up speed, the force of his resistance is by using Newton's laws, the force of air resistance can be found from the law of conservation of mechanical energy and special aerodynamic formulas.
You will need
• rangefinder, scale, speedometer or radar, ruler, stopwatch.
Instruction
1
The definition of air resistance a falling body uniformly Measure body weight using a scale. Dropping it from some height, make sure it is moving evenly. Multiply body weight in kg by the acceleration due to gravity, (9.81 m/S2), the result is the force of gravity acting on the body. And since it moves uniformly and rectilinearly, gravity will be equal to the force of air resistance.
2
The definition of air resistance the body will skorostrel gaining body mass by using weights. After the body began to move, using a speedometer or radar measure its instantaneous initial velocity. In the end, measure its instantaneous final velocity. Speed is measure in metres per second. If you measure it in kilometers per hour, divide the value by 3.6. In parallel to using the stopwatch to measure the time in which occurred the change. Subtracting the final speed from the start and dividing the result by the time, find the acceleration with which the body moves. Then find the force that causes a body to change velocity. If the body falls, then it is gravity, if the body moves horizontally, the thrust of the engine. From this power subtract the weight of a body on its acceleration (Fc=F+m•a). This will be the force of air resistance. It is important that the body did not touch the ground, for example, moving on an air cushion or fallen down.
3
Determination of air resistance to a body falling from vicotiasecret body weight and drop it from a height, which is known in advance. Upon contact with the surface of the earth clamp the velocity of the body using a speedometer or radar. Then find the product of the gravitational acceleration 9.81 m/S2 on the height from which the falling body, subtract from this value the speed squared. The result, multiply by body weight and divide by the height from which it fell (Fc=m•(9,81•H-v2)/H). This will be the force of air resistance.