Master Newton's laws and force analysis. Calculate normal force, friction, momentum, and more.
🔥 Popular Calculations
Calculate force using Newton's Second Law (F=ma).
Open CalculatorCalculate the normal force acting on an object on various surfaces.
Open CalculatorCalculate static and kinetic friction forces between surfaces.
Open CalculatorCalculate momentum of an object using mass and velocity.
Open CalculatorCalculate the tension force in ropes, cables, or strings.
Open CalculatorCalculate impulse and change in momentum.
Open CalculatorCalculate the sum of all forces acting on an object.
Open CalculatorCalculate weight force from mass and gravity.
Open CalculatorCalculate the ideal banking angle for curved roads or tracks.
Open CalculatorEstimate the impact force in a vehicle collision.
Open CalculatorAnalyze collisions using the principle of conservation of momentum.
Open CalculatorCalculate the Coriolis force in a rotating reference frame.
Open CalculatorCalculate forces and acceleration on an inclined plane.
Open CalculatorConvert mass in kilograms to weight force in Newtons.
Open CalculatorDetailed calculator for F=ma, solving for force, mass, or acceleration.
Open CalculatorUnderstand action and reaction forces in interactions.
Open CalculatorCalculate the force resisting the motion of a rolling body.
Open CalculatorDynamics is the branch of mechanics concerned with the motion of bodies under the action of forces. While kinematics simply describes "how" things move (velocity, acceleration), dynamics explains "why" they move. It is the study of cause and effect. The central concept in dynamics is force—an interaction that causes an object to change its motion or shape.
At the heart of classical dynamics lie Sir Isaac Newton's three laws of motion, published in 1687. These laws form the foundation of classical mechanics and are sufficient to describe the motion of everything from sand grains to planets (at non-relativistic speeds). Dynamics connects the abstract concepts of acceleration to tangible physical quantities like mass, force, and momentum.
Engineers use dynamics to design safer cars, stable bridges, and efficient engines. It allows us to understand why it's harder to stop a heavy truck than a bicycle, how a rocket generates thrust in the vacuum of space, and why banking a road curve prevents cars from sliding off. Our calculators below help you quantify these forces, but grasping the underlying principles is essential for true understanding.
Inertia is the resistance of any physical object to any change in its
velocity. This includes changes to the object's speed or direction of motion. An object at
rest wants to stay at rest; an object in motion wants to stay in motion.
Mass is the quantitative measure of inertia. The more mass an object has,
the more force is required to change its motion. It is crucial to distinguish mechanics from
weight. Mass is intrinsic (depends on atoms), while weight is extrinsic (depends on
gravity).
"An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force." This explains why you fly forward when a car brakes suddenly—your body wants to keep moving.
This is the most famous equation in dynamics. It states that the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. Force causes acceleration; mass resists it.
Friction is a resistive force that opposes relative motion between surfaces.
Static Friction: Prevents stationary objects from starting to move. It is
usually stronger than kinetic friction.
Kinetic Friction: Acts on moving objects, slowing them down.
Without friction, we couldn't walk, cars couldn't drive, and nails wouldn't hold wood
together.
Dynamics relies heavily on vector mathematics. Forces must be resolved into components (x and y axes) to be summed correctly. Here are the fundamental equations used in our calculators:
Variables: F=Force (N), m=Mass (kg), a=Acceleration (m/s²), g=Gravity (9.81 m/s²), μ=Coefficient of friction, N=Normal force, p=Momentum (kg·m/s), J=Impulse (N·s).
Roller coasters use dynamics to thrill riders safely. The "weightless" feeling is actually a result of the normal force becoming zero at the top of a loop, while the crushing feeling at the bottom is due to heavy g-forces (high normal force).
Statics (a subset of dynamics where acceleration is zero) keeps buildings standing. Engineers calculate the net forces on every beam and column to ensure the sum is zero, preventing collapse under wind or earthquake loads.
Newton's Third Law is the principle behind rocket propulsion. By expelling gas at high speed backward (action), the rocket receives an equal and opposite thrust forward (reaction). No air is needed to "push against."
Mass is a measure of how much matter is in an object (measured in kg). It remains constant wherever you are in the universe. Weight is the force of gravity acting on that mass (measured in Newtons). On the Moon, your mass would be exactly the same, but your weight would be 1/6th of what it is on Earth because gravity is weaker.
The word "Normal" in geometry means "perpendicular." The Normal Force is the contact support force exerted by a surface (like a table or floor) against an object resting on it. It always acts perpendicular to the surface. It prevents the object from passing through the surface. It is not always equal to gravity (e.g., in an elevator or on a ramp).
This is a common misconception! Newton's 3rd Law says "For every action, there is an equal and opposite reaction." It might seem like they cancel to zero. However, action and reaction forces act on different objects. If you kick a ball, your foot exerts force on the ball, and the ball exerts force on your foot. To analyze the ball's motion, we only look at the force on the ball. The reaction force acts on you, not the ball, so it doesn't cancel the kick.
On a microscopic level, surfaces are rough, with peaks and valleys (asperities). When two surfaces slide past each other, these irregularities weld together and break apart, converting kinetic energy into heat. Electromagnetic forces between atoms also play a significant role.
On a flat road, friction alone provides the centripetal force to turn a car. If it's icy, friction drops, and the car skids. By banking (tilting) the road, a component of the Normal Force points horizontally toward the center of the turn. This allows the car to turn even with zero friction if the speed is right!
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