Unit 1: Forces and Energy Lesson 1: Forces and Motion Lesson 1: Forces and Motion Acceleration Force Describe motion and its factors. Explain speed, velocity and acceleration. Relate the forces to the above terms. Compare balanced and unbalanced forces Friction Inertia Motion Speed Velocity State the definitions of gravity and friction forces Lesson 1: Forces and Motion • What did you notice about the sky diver? • How does their position affect their fall? • Would splaying their arms and legs affect their speed? • How would their fall change if their parachutes open? Lesson 1: Forces and Motion • What if the sky diver opened the parachute? Lesson 1: Forces and Motion • By changing the shape and position of their bodies, the skydivers can change the speed at which they fall. • They fall slowest in belly-to-Earth position because the drag force is greatest. • They fall fastest when they streamline their bodies and minimize drag. Lesson 1: Forces and Motion • • • • • • The position of an object is its location. Motion is a change in an object’s position. Motion of an object is related to: Its distance covered Its direction Its time passed Lesson 1: Forces and Motion • The speed of an object is how fast an object position changes over time. • Unit of speed is distance per time • (m/s) meter per second • (km/h) kilometers per hour Lesson 1: Forces and Motion • Velocity is the speed and the direction of an object. • Velocity have the same unit of speed but it should include the direction. • Ex : plane is flying 640 km/h This is the speed. • Ex: plane is flying 640 km/h south This is the velocity. Lesson 1: Forces and Motion • Acceleration a change in velocity over time. • When an object speeds up, slows down, or change its direction it accelerates. • And only sometimes if its direction changes it accelerate. Lesson 1: Forces and Motion Increase Decrease Change its direction Lesson 1: Forces and Motion • A force is any push or pull. • The acceleration of an object depends on how much force is there. • More force more acceleration • Less force less acceleration • Also acceleration depends on weight of an object. • More weight less acceleration Lesson 1: Forces and Motion Lesson 1: Forces and Motion • P: 12 # 1: • What two factors affect acceleration? • Force and Weight • P: 12 # 2: • How would you increase the speed of a toy car? • Increase the force of push or decrease the weight of the car. Lesson 1: Forces and Motion • Forces that add up on same directions produce stronger force. • Forces that add up in opposite directions produce weaker force. • Total forces on an object is the sum of all forces acting on the object. Lesson 1: Forces and Motion • Forces acting on object without changing its motion is called balanced forces. • Objects at rest • Objects in motion but not accelerating • Sum of forces on this object should be equal to zero. Lesson 1: Forces and Motion • Forces that do not add up to zero are unbalanced forces. • Change in motion • Change in speed • Change in direction Lesson 1: Forces and Motion • • • • Sum is zero Sum is not zero No acceleration Change in direction, motion and speed. Balanced forces Unbalanced forces Lesson 1: Forces and Motion • Inertia is the tendency of an object in motion to stay in motion or of an object at rest to stay at rest. Lesson 1: Forces and Motion • Gravity and friction are two forces that can act on an object. • Gravity is a non contact force that pulls the objects toward each other. • Friction is a contact force that slows or stops the objects from moving.