Newton's First Law

Newton's First Law of Motion

• An object at rest stays at rest unless acted upon by an unbalanced force.
• An object in motion continues in motion with the same velocity unless acted upon by a net force.
• Balanced forces result in a net force of zero, leading to an object remaining at rest or in constant motion.
• Weight force calculation involves multiplying mass (in kilograms) by gravitational acceleration (9.8 m/s²).
• Normal force, exerted by a surface, counteracts the weight force to maintain an object's rest.
• Friction counters motion, causing moving objects to decelerate and eventually halt if a net frictional force exists.
• Absence of friction allows an object in motion to persist indefinitely.
• Outer space offers a near-frictionless environment, enabling prolonged object movement.
• An object at rest indicates a net force of zero acting upon it.
• Constant velocity motion also implies a net force of zero.
• Non-zero net force leads to acceleration, which is a change in velocity.

Newton's Second Law of Motion

• Net force on an object equals its mass multiplied by its acceleration (F = ma).
• Acceleration is the change in velocity divided by the change in time.
• With constant net force, increasing mass decreases acceleration, and vice versa.
• Doubling mass at constant acceleration doubles the force.
• Doubling acceleration at constant mass doubles the force.
• Tripling both mass and acceleration increases the force ninefold.
• Momentum, the product of mass and velocity, represents an object's quantity of motion.
• An object at rest possesses zero momentum, while a moving object has momentum.
• Greater mass or velocity equates to greater momentum.
• Net force equals the rate of change of momentum with respect to time is an alternate expression of Newton's Second Law.
• Impulse is the product of force and time, equivalent to the change in momentum.
• The impulse-momentum theorem equates the impulse applied to an object with its change in momentum.

Newton's Third Law of Motion

• Every action elicits an equal and opposite reaction.
• Jumping and throwing a basketball exemplifies this, where force on the ball results in recoil on the person.
• Throwing a ball to the right on a boat causes the person and boat to move left.
• Forces remain the same between two objects, but objects with smaller mass experience greater acceleration under constant force.
• In space, throwing an object in one direction propels you in the opposite direction.

Problem Solving Examples

• A car moving at a constant velocity is subject to a net force of zero.
• A 1500 N frictional force on a car necessitates a 1500 N engine force to maintain constant velocity.
• Applying 200 N of force to a 10 kg box on a frictionless surface results in an acceleration of 20 m/s².
• The box attains a speed of 160 m/s² after 8 seconds under these conditions.
• Applying 300 N of force with a 200 N frictional force yields a net force of 100 N.