NJC Projectile motion notes

National Junior College Science Department | Physics 1 5. PROJECTILE MOTION Content Page 5. Projectile Motion .......................................................................................................... 1 5.1 Free fall ..................................................................................................................... 2 5.1.1 What is weight? .................................................................................................. 2 5.1.2 Projectile Motion ................................................................................................. 3 5.2 Gravitational potential energy in a uniform field ........................................................ 9 5.3 Effects of air resistance ........................................................................................... 10 Learning Objectives 5.1 Free fall (a) Describe and use the concept of weight as the force experienced by a mass in a gravitational field. (b) Describe and explain motion due to a uniform velocity in one direction and a uniform acceleration in a perpendicular direction. 5.2 Gravitational potential energy in a uniform field (c) Derive, from the definition of work done by a force, the equation ߂ܧ௣=߂݃݉ℎ for gravitational potential energy changes in a uniform gravitational field (e.g. near the Earth’s surface). (d) Recall and use the equation ߂ܧ௣=߂݃݉ℎ to solve problems. 5.3 Effects of air resistance (e) Describe qualitatively, with reference to forces and energy, the motion of bodies falling in a uniform gravitational field with air resistance, including the phenomenon of terminal velocity.

National Junior College Science Department | Physics 2 5.1 FREE FALL 5.1.1 What is weight? (a) Describe and use the concept of weight as the force experienced by a mass in a gravitational field. Weight is the force experienced by an object due to the gravitational attraction exerted on it by a massive body, such as the Earth. It can be described using the following formula: W = mg Where:  W is the weight of the object (in newtons, N),  m is the mass of the object (in kilograms, kg),  g is the gravitational field strength ( in N kg1 ), which is approximately 9.81  N kg1, near the Earth's surface. Question : Show gravitational field strength is numerically equal to acceleration of free fall. For an object to be in free fall, the only force acting on it is the gravitational force acting on the body or its weight. Resultant Force = Weight ma = mg a = g Where:  a is the acceleration of free fall. Therefore, gravitational field strength is numerically equal to acceleration of free fall. The concept of weight arises because gravity pulls objects toward the center of a massive body, like Earth. The force of gravity, on an object, depends on two things: 1. Mass of the object (m): The more massive an object, the greater the gravitational pull it will experience. 2. Gr