# Facts about Velocity for Kids

• Speed describes only how fast an object is moving, whereas velocity gives both how fast and in what direction the object is moving.
• If a car travels at 60 km/h, its speed is known.
• To have a constant velocity, an object must have a constant speed and motion in a constant direction.
• The scalar absolute value (magnitude) of velocity is speed, a quantity that is measured in meters per second when using the SI (metric) system.
• The average velocity v of an object moving through a displacement during a time interval is described by the formula: the error analysis will look like this The velocity vector v of an object that has positions x(t) at time t and x at time, can be computed as the derivative of position: Velocity is also defined as rate of change of displacement.
• Slope of tangent of position or displacement time graph is instantaneous velocity and its slope of chord is average velocity.
• The equation for an object’s velocity can be obtained mathematically by evaluating the integral of the equation for its acceleration beginning from some initial period time to some point in time later.
• This can be expanded to give the position at any time t in the following way: These basic equations for final velocity and position can be combined to form an equation that is independent of time, also known as Torricelli’s equation: The above equations are valid for both Newtonian mechanics and special relativity.
• In particular, in Newtonian mechanics, all observers agree on the value of t and the transformation rules for position create a situation in which all non-accelerating observers would describe the acceleration of an object with the same values.
• In Newtonian mechanics, the kinetic energy, of a moving object is linear with both its mass and the square of its velocity: The kinetic energy is a scalar quantity.
• Escape velocity is the minimum velocity a body must have in order to escape from the gravitational field of the earth.
• Relative velocity is a measurement of velocity between two objects as determined in a single coordinate system.
• Relative velocity is fundamental in both classical and modern physics, since many systems in physics deal with the relative motion of two or more particles.
• This is not the case anymore with special relativity in which velocities depend on the choice of reference frame.
• In the one dimensional case, the velocities are scalars and the equation is either: In polar coordinates, a two-dimensional velocity is described by a radial velocity, defined as the component of velocity away from or toward the origin.
• The radial and angular velocities can be derived from the Cartesian velocity and displacement vectors by decomposing the velocity vector into radial and transverse components.
• The transverse velocity is the component of velocity along a circle centered at the origin.
• such that Angular momentum in scalar form is the mass times the distance to the origin times the transverse velocity, or equivalently, the mass times the distance squared times the angular speed.
• The sign convention for angular momentum is the same as that for angular velocity.