Answer:
84.83 ft/s^2 or 85 ft/s^2
Step-by-step explanation:
A = Δ v Δ t
Acceleration is the rate of change of an objects speed; in other words, it's how fast velocity changes. According to Newton's second law, acceleration is directly proportional to the summation of all forces that act on an object and inversely proportional to its mass. It's all common sense - if several different forces are pushing an object, you need to work out what they add up to (they may be working in different directions), and then divide the resulting net force by your object's mass.
This acceleration definition says that acceleration and force are, in fact, the same thing. When the force changes, acceleration changes too, but the magnitude of its change depends on the mass of an object. This is not true in a situation when the mass also changes, e.g., in rocket thrust, where burnt propellants exit from the rocket's nozzle.
In the 17th century, Sir Isaac Newton, one of the most influential scientists of all time, published his famous book Principia. In it, he formulated the law of universal gravitation which states that any two objects with mass will attract each other with a force exponentially dependent on distance between these objects (specifically, it is inversely proportional to the distance squared). The heavier the objects are, the greater is gravitational force. It explains, for example, why planets orbit around the very dense Sun.
In Principia, Newton also includes three laws of motion which are central to understanding the physics of our world. The acceleration calculator is based on three various acceleration equations, where the third is derived from Newton's work:
a = (v_f - v_i) / Δt,
a = 2 * (Δd - v_i * Δt) / Δt²,
a = F / m,
where:
a is the acceleration,
v_i and v_f are respectively the initial and final velocities,
Δt is the acceleration time,
Δd is the distance traveled during acceleration,
F is the net force acting on an object that accelerates,
m is the mass of this object.
If you already know how to calculate acceleration let's focus on the units of acceleration. You can derive them from the equations we listed above. All you need to know is that speed is expressed in feet per second (imperial/US system) or in meters per second (SI system) and time in seconds. Therefore, if you divide speed by time (as we do in the first acceleration formula), you'll get acceleration unit ft/s² or m/s² depending on which system you use.
Alternatively, you can use the third equation. In this case, you need to divide force (poundals in US and newtons in SI) by mass (pounds in US and kilograms in SI) obtaining pdl/lb or N/kg. They both represent the same thing, as poundal is pdl = lb * ft/s² and the newton is N = kg * m/s². When you substitute it and reduce the units, you'll get (lb * ft/s²) / lb = ft/s² or (kg * m/s²) / kg = m/s².
There is also a third option that is, in fact, widely used. You can express acceleration by standard acceleration, due to gravity near the surface of the Earth which is defined as g = 31.17405 ft/s² = 9.80665 m/s². For example, if you say that an elevator is moving upwards with the acceleration of 0.2g, it means that it accelerates with about 6.2 ft/s² or 2 m/s² (i.e., 0.2*g).