Speed is a physical quantity defined as a function of time and direction. Often, when faced with physics problems, you will need to calculate the initial speed (speed of motion and direction) at which a given object began its movement. There are multiple equations that can be used to determine the initial velocity of an object. Based on the data provided by the problem, you can choose the most suitable equation to find the solution quickly and easily.
Steps
Method 1 of 4: Calculate the Initial Speed Knowing the Final Speed, Acceleration and Time
Step 1. Learn to determine the correct equation
In order to successfully solve any physics problem, you need to know which equation to use based on known information. Writing all the initial data provided by the problem is the first step to be able to identify the best equation to use. If the information you have is final speed, acceleration and time taken, you can use the following formula:
- Initial Speed: V.the = Vf - (a * t).
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Understand the meaning of the symbols in the equation.
- V.the represents the "Initial Speed".
- V.f represents the "Final Speed".
- a represents "acceleration".
- t represents "time".
- Note: This formula represents the standard equation used to determine the starting velocity of an object.
Step 2. Use the already known data
After you have transcribed the initial information provided by the problem to be solved and have identified the correct equation to use, you can replace the variables of the formula with the appropriate data. Setting each step carefully to find the solution to your problem is a very important process.
If you make a mistake, you will be able to spot it quickly by carefully observing all the previous steps
Step 3. Solve the equation
When all numeric values are entered in the correct position, solve the equation respecting the hierarchical order of each operation to be performed. If allowed, use a calculator to help minimize possible miscalculations.
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For example: an object accelerates east to 10 m / s2 and, after 12 seconds, it reaches the final speed of 200 m / s. Calculate the initial velocity of the object.
- Start by writing down the known information:
- V.the =?, Vf = 200 m / s, a = 10 m / s2, t = 12 s.
- Multiply the acceleration by the time: a * t = 10 * 12 = 120.
- Subtract the result of the previous calculation from the final speed: V.the = Vf - (a * t) = 200 - 120 = 80; V.the = 80 m / s ext.
- Write the solution to the problem correctly. Remember to always include the units of measurement, normally meters per second m / s, as well as the direction the object is moving in. Without providing information about the direction in which the object is moving, you are not describing its speed of movement, but simply the absolute value of that information.
Method 2 of 4: Calculate Initial Speed Knowing Distance Traveled, Time and Acceleration
Step 1. Learn to determine the correct equation
In order to successfully solve any physics problem, you need to know which equation to use based on known information. Writing all the initial data provided by the problem is the first step in identifying the best equation to use. If the information you have is distance traveled, time taken and acceleration, you can use the following equation:
- Initial Speed: V.the = (d / t) - [(a * t) / 2].
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Understand the meaning of the symbols in the equation.
- V.the represents the "Initial Speed".
- d represents the "distance".
- a represents "acceleration".
- t represents "time".
Find Initial Velocity Step 5 Step 2. Use already known data
After you have transcribed the initial information provided by the problem to be solved and have identified the correct equation to use, you can replace the variables of the formula with the appropriate data. Setting each step carefully to find the solution to your problem is a very important process.
If you make a mistake, you will be able to spot it quickly by carefully observing all the previous steps
Find Initial Velocity Step 6 Step 3. Solve the equation
When all numeric values are entered in the correct position, solve the equation respecting the hierarchical order of each operation to be performed. If allowed, use a calculator to help minimize possible miscalculations.
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For example: an object accelerates westward at 7 m / s2 covering 150 m in 30 seconds. Calculate the initial velocity of the object.
- Start by writing down the known information:
- V.the =?, d = 150 m, a = 7 m / s2, t = 30 s.
- Multiply the acceleration by the time: a * t = 7 * 30 = 210.
- Divide the result in half: (a * t) / 2 = 210/2 = 105.
- Divide the distance by the time: d / t = 150/30 = 5.
- Now subtract the first quotient from the second: V.the = (d / t) - [(a * t) / 2] = 5 - 105 = -100 Vthe = -100 m / s west.
- Write the solution to the problem correctly. Remember to always include units of measurement, normally meters per second m / s, as well as the direction the object is moving in. Without providing information about the direction in which the object is moving, you are not describing its speed of movement, but simply the absolute value of that information.
Method 3 of 4: Calculate the Initial Speed Knowing the Final Speed, Acceleration and Distance Traveled
Find Initial Velocity Step 7 Step 1. Learn to determine the correct equation
In order to successfully solve any physics problem, you need to know which equation to use based on known information. Writing all the initial data provided by the problem is the first step in identifying the best equation to use. If the information you have is final speed, acceleration and distance traveled you can use the following equation:
- Initial Speed: V.the = √ [Vf2 - (2 * a * d)].
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Understand the meaning of the symbols in the equation.
- V.the represents the "Initial Speed".
- V.f represents the "Final Speed".
- a represents "acceleration".
- d represents the "distance".
Find Initial Velocity Step 8 Step 2. Use already known data
After you have transcribed the initial information provided by the problem to be solved and have identified the correct equation to use, you can replace the variables of the formula with the appropriate data. Setting each step carefully to find the solution to your problem is a very important process.
If you make a mistake, you will be able to spot it quickly by carefully observing all the previous steps
Find Initial Velocity Step 9 Step 3. Solve the equation
When all numeric values are entered in the correct position, solve the equation respecting the hierarchical order of each operation to be performed. If allowed, use a calculator to help minimize possible miscalculations.
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For example: an object accelerates northward at 5 m / s2 and, after 10 m, it reaches the final speed of 12 m / s. Calculate the initial velocity of the object.
- Start by writing down the known information:
- V.the =?, Vf = 12 m / s, a = 5 m / s2, d = 10 m.
- Calculate the square of the final speed: V.f2 = 122 = 144.
- Multiply the acceleration by the distance, then double the result: 2 * a * d = 2 * 5 * 10 = 100.
- Subtract the product obtained in the previous step from the product obtained in the first: V.f2 - (2 * a * d) = 144 - 100 = 44.
- To find the solution to the problem, calculate the square root of the result obtained: = √ [Vf2 - (2 * a * d)] = √44 = 6.633 Vthe = 6.633 m / s north.
- Write the solution to the problem correctly. Remember to always include the units of measurement, normally meters per second m / s, as well as the direction the object is moving in. Without providing information about the direction in which the object is moving, you are not describing its speed of movement, but simply the absolute value of that information.
Method 4 of 4: Calculate the Initial Speed Knowing the Final Speed, Time and Distance Traveled
Find Initial Velocity Step 10 Step 1. Learn to determine the correct equation
In order to successfully solve any physics problem, you need to know which equation to use based on known information. Writing all the initial data provided by the problem is the first step in identifying the best equation to use. If the information you have is final speed, time and distance traveled you can use the following equation:
- Initial Speed: V.the = Vf + 2 (d / t).
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Understand the meaning of the symbols in the equation.
- V.the represents the "Initial Speed".
- V.f represents the "Final Speed".
- t represents "time".
- d represents the "distance".
Find Initial Velocity Step 11 Step 2. Use the already known data
After you have transcribed the initial information provided by the problem to be solved and have identified the correct equation to use, you can replace the variables of the formula with the appropriate data. Setting each step carefully to find the solution to your problem is a very important process.
If you make a mistake, you will be able to spot it quickly by carefully observing all the previous steps
Find Initial Velocity Step 12 Step 3. Solve the equation
When all numeric values are entered in the correct position, solve the equation respecting the hierarchical order of each operation to be performed. If allowed, use a calculator to help minimize possible miscalculations.
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For example: an object reaches the final speed of 3 m / s after traveling southbound a distance of 15 m in 45 seconds. Calculate the initial velocity of the object.
- Start by writing down the known information:
- V.the =?, Vf = 3 m / s, t = 45 s, d = 15 m.
- Divide the distance by the time: (d / t) = (45/15) = 3
- Multiply the result by 2: 2 (d / t) = 2 (45/15) = 6
- Subtract the final velocity from the result: 2 (d / t) - Vf = 6 - 3 = 3 Vthe = 3 m / s south
- Write the solution to the problem correctly. Remember to always include the units of measurement, normally meters per second m / s, as well as the direction the object is moving in. Without providing information about the direction in which the object is moving, you are not describing its speed of movement, but simply the absolute value of that information.
