TJC Unit 5 Projectile Motion

i Unit 5: Projectile Motion Learning Outcomes (a) describe and use the concept of weight as the force experience 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. (c) derive, from the definition of work done by a force, the equation ∆Ep = mg∆h for gravitational potential energy changes in a uniform gravitational field (e.g. near the Earth’s surface). (d) recall and use the equation ∆Ep = mg∆h to solve problems. (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. Name : ________________________________ Class : _________

5.1 Weight LO(a) In unit 3, we saw that all objects released near the surface of the Earth fall with the same acceleration (the acceleration of free fall) if air resistance can be neglected. The force causing this acceleration is the gravitational attraction of the Earth on the object. The gravitational force which acts on an object is called the weight of the object. We can apply Newton’s second law to the weight. For a body of mass m falling with the acceleration of free fall g, the weight W is given by W mg= The SI unit of force is the newton (N). This is also the unit of weight. Because weight is a force and force is a vector, we ought to be aware of the direction of the weight of an object. It is towards the centre of the Earth. mass weight a measure of the inertia of a body a measure of the gravitational force on a body SI unit: kg SI unit: N same regardless of location varies with gravitational field strength at each location Example 1 A boy throws a ball vertically upwards. It rises to a maximum height, where it is momentarily at rest, and falls back to his hands. Which of the following gives the acceleration of the ball at various stages in its motion? Take vertically upwards as positive. Neglect air resistance. rising at maximum height falling A −9.81 m s-2 0 +9.81 m s-2 B −9.81 m s-2 −9.81 m s-2 −9.81 m s-2 C +9.81 m s-2 +9.81 m s-2 +9.81 m s-2 D +9.81 m s-2 0 −9.81 m s-2 Weight is the force experience by a mass in a gravitational field.

5.2 Projectile Motion LO(b) So far we have been dealing with motion along a straight line; that is, one-dimensional motion. We will now look at the motion of particles moving in paths in two dimensions. The stroboscopic photographs below depicts three balls A, B and C released simultaneously. Bal