# Advice 1: How to find the mass, knowing the force

The force can act only on the material body, which certainly has a lot. Using Newton's second law, we can determine the mass of the body which is affected by the force. Depending on the nature of the force to determine mass through strength you may need additional values.
You will need
• - accelerometer;
• roulette;
• - stopwatch;
• calculator.
Instruction
1
To calculate body mass is influenced by the well-known strength, use ratio of which is derived from Newton's second law. To do this, using the accelerometer measure the acceleration, which received the body as a result of impact forces. If this device is not available, measure the speed at the beginning and end of the observation time and divide the change in speed on time. This will be the average acceleration of a body over a measured period of time. Calculate the weight by dividing the value of the force acting on the body F, measured in m/S2 the acceleration of a, m=F/a. If the value of the force to take in Newtons, the mass will receive in kilograms.
2
Calculate the weight of the body on which the force of gravity. To do this, hang it on the dynamometer and on a scale, determine the force that acts on the body. This will be the force of gravity. To determine body weight, the value of this force is Ft divide by the gravitational acceleration g≈9.81 m/S2 m=F/g. For convenience in calculations it is possible to take the value of g≈10 m/S2 in the case that you don't need high accuracy mass values in kilograms.
3
When the body moves on a circular path with constant speed, it is also the force. If you know its value, find the mass of a body moving along a circular path. For this measure or calculate the velocity of a body. The measure speedometer if possible. To calculate speed, measure the radius of the trajectory of a body with a tape measure or a ruler R and the time of a full revolution T with the aid of a stopwatch, it is called period of rotation. The speed will be equal to the product of the radius by the number of 6.28 divided by the period. Find the mass by multiplying the force F on the radius of the path of movement of the body and dividing the result by the square of its velocity m=F•R/v2. To get the result in kilograms, the speed is measure in metres per second, the radius in meters and force in Newtons.

# Advice 2: How to find the time, knowing the speed

Tasks on kinematics, which is necessary to calculate speed, time or path of a uniformly and rectilinearly moving bodies, meet in the school course of algebra and physics. For their solution find it in the condition values, which can be interconnected to equalize. If the condition is required to determine the time at a known speed, use the following instructions.
You will need
• - handle;
• paper for records.
Instruction
1
The simplest case is the motion of a body with a given uniform velocityu. Know the distance that the body has passed. Find time in transit: t = S/v, h, where S is distance, v is the average velocity of the body.
2
The second example is for a counter motion. From point A to point b the car is moving with speedu 50 km/h. to Meet him from point B at the same time I left the moped with the speedu 30 km/h. The distance between the points A and b 100 km is Required to find the timethrough which they will meet.
3
Designate a meeting point with the letter K. Let the distance of AK, who drove the car be x km. Then the path of the rider will amount to 100's of km. From the problem statement it follows that the time in the way of car and motorbike alike. Write down the equation: x/v = (S-x)/v’, where v, v’ – vehicle speed, and a moped. Substituting the data solve the equation: x = 62,5 km. Now find the time: t = for 62.5/50 = 1.25 hours or 1 hour and 15 minutes.
4
The third example – given the same conditions, but left 20 minutes late the bike. To determine how much time will the car before meeting with a moped.
5
Write down the equation, similar to the previous one. But in this case time of a moped in the path will be 20 minutes more than the car. For the adjustment of the parts, subtract one-third of the hours from the right side of the expression: x/v = (S-x)/v’-1/3. Find the x – 56,25. Calculate time: t = 56,25/50 = 1,125 hours, or 1 hour 7 minutes 30 seconds.
6
The fourth example is a challenge for a body moving in one direction. Car and moped with the same speed move from point A. it is Known that the car left half an hour later. After a time he will catch up with the moped?
7
In this case, the same will be the distance traveled of the vehicle. Let time in the path of the car be x hours then time in the path of the moped will be x+0,5 hours. You got the equation: vx = v’(x+0,5). Solve the equation, substituting the value of speed, and find x – 0.75 hour or 45 minutes.
8
The fifth example is a car and a moped with the same speed moving in the same direction, but the moped went from point b, located at a distance of 10 km from point A, half an hour earlier. To calculate, through what time after the start of the car will overtake the moped.
9
The distance that the car drove 10 km more. Add this difference to the path of the motorcycle and align the parts of the expression: vx = v’(x+0,5)-10. Substituting the values of speed and solved it, you will get the answer: t = 1.25 hours or 1 hour and 15 minutes.
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