Kinetics of a Particle: Force and Acceleration

Particle motion can be written in rectangular coordinates or cylindrical coordinates, depending on the path of the particle. In classical mechanics, the coordinate system you choose helps describe how a particle moves in an inertial frame.

When motion stays in the x-y plane, rectangular components are often enough. Using only x and y makes the equation easier to write and follow. This form works well for motion that does not need a third spatial direction.

Curved paths often call for...

Curved motion is described by splitting a particle’s acceleration into tangential and normal parts. These two components help show how the particle moves along a curving path at a specific point.

The tangential component lies along the curve. It shows how the speed changes with time. A positive tangential acceleration means the speed is increasing. A negative tangential acceleration means the speed is decreasing.

The normal component points along the radial direction of the curve. It...

Chair reaction forces in curvilinear motion are found by using tangential and normal components of acceleration. A 70 kg man sits upright in a chair that is connected to a pin support by member BC. The member is 10 m long, and it makes a 45° angle with the horizontal at the instant of interest.

The man has a speed of 5 m/s, and that speed is increasing at 1 m/s². The tangential acceleration is therefore 1 m/s². The normal acceleration is then determined from the tangential speed and the radius...

The center of mass helps describe the motion of a system of particles. For a group with n particles, the equation of motion can be extended from a single particle to the whole system. Each particle has a net force on it that comes from both internal forces and external forces.

When the motion of all particles is combined, the system follows one equation of motion. Forces between pairs of particles are internal forces. These forces act along the same line, have equal magnitude, and point in...

Central force motion describes the path of an object acted on by a force that points toward a fixed point, usually the origin. The force size depends on how far the object is from that point. For a mass m, the motion is written in polar coordinates, which use distance and angle instead of x and y position.

In this system, the azimuthal component of force is zero. That means there is no force in the angular direction. When the equation of motion is rewritten and integrated, the product of the...