Transcript Do Now
Topic: Forces and Motion Aim: How do you get an object to start moving? Do Now: Complete question # 3 on back of the KE and PE packet. HW:CL Waves due Thursday Reading Notes – Newton’s Laws Energy and Waves Exam on Tuesday At which two points on the pendulum, is the pendulum experiencing the greatest potential energy? Identify the two processes below. Support your answer. Which of the following electromagnetic waves have the highest frequency? 1. Visible light 2. Ultraviolet light 3. Microwaves 4. Infrared waves Identify the statement that is true based of the electromagnetic spectrum. 1. Microwaves are shorter then X-rays. 2. Infrared rays are longer than gamma waves. 3. Radio waves are longer than visible light waves. 4. UV waves are longer than visible light waves. 5. Visible light rays are shorter than microwaves . 6. Red rays have a shorter waves that violet rays. Which type of EW are used in medical technology because they can pass through parts of the human body? 1. Microwaves 2. X-rays 3. Infrared waves 4. Ultraviolet radiation Force • • • • A push or a pull Newtons = N Gives energy to an object Move , stop, or change direction Work: • F xd – F = force applied – D = distance the object moved • Work is done when force causes motion. Inertia • An object’s resistance to change in motion What causes the force of inertia? • Combination of gravity pulling down on an object and friction resisting a push ahead The body is motionless at the start of a race. The athlete must overcome their inertia to start moving! • Motion is caused by Unbalanced a greater force Forces (Unequal) Balanced • No motion occurs Forces (EQUAL) Friction • Force that resists the relative motion of 2 bodies in direct contact • Acts opposite to motion of moving object • Causes moving object to slow down & stop •Generates heat Lubricant: Slippery substances • Oil or grease • Decreases friction ICE = very slippery = –DECREASES friction • STICKY SURFACE = hard to move –A lot of friction Examples: 1. Gymnasts use chalk on hands to increase friction. 2. Cyclists rely on friction to hold their bikes on the ground during turns. 3. Without friction cars would not be able to stop. Why is water being added to the slip & slide? What would happen if water was not added? The driver of the car applies the brakes to avoid hitting the cow. But how does this cause the car to slow down and stop? The brakes cause the wheels to stop turning and to slide on the road surface. This action produces a force that resists the forward movement of the car. This force is called friction. 25N 15N 25N + 15N = 40N to the right 25N 15N 25N - 15N = 10N to the left 10N 10N 10N 5N Let’s summarize… 1. Describe force. 2. Describe work. 3. How do you know when work is done? 4. Explain the difference between balanced and unbalanced forces. 5. Describe friction. 6. What kind of surface will decrease friction? Increase friction? 7. How do you calculate total force when applying force on an object in the same direction? 8. How do you calculate total force when applying force on an object in the different directions? Which way will the object move? Bw 2 rarefactions Bw 2 compressions Describe a wavelength in a longitudinal wave. The distance between 2 compressions OR 2 rarefactions. C B AA to keep track of units in multi-step conversion problems D Identify the parts of this transverse wave. (Click to uncover the answer of each letter) 1. Which wave has the highest frequency? A C 2. Which wave has the longest wavelength? A B C Consider a cart on a horizontal frictionless table. Once the cart has been given a push and released, what will happen to the cart? 1. 2. 3. 4. 5. slowly come to a stop continue with constant acceleration continue with decreasing acceleration continue with constant velocity immediately come to a stop A test paper is sitting at rest on your desk. Which of the following statements best describes this situation? 1. There are no forces acting on your paper. 2. Your paper is at rest in any coordinate system. 3. Your paper exerts no force on the desk. 4. There are several forces acting on your paper, but they balance each other out. A 2 ton elephant is balancing on a tree trunk. Which of the following statements is accurate? 1. The weight of the tree stump is greater than 2 tons. 2. A 4 ton force on the ground spreads out in all directions. 3. The tree stump is exerting a 2 ton force upward on the elephant. 4. The downward force on the ground under the tree stump is 4 tons. A hot air balloon exerts a force of 1200N while lifting a load of 800 N. Which free-body force diagram depicts the forces involved? 400N 1. 800N 800N 1200N 2. 3. 1200N 800N 800N 4. 400N A student is riding a bike and applies the brakes. What most helps the bike to stop? 1. Friction 2. Heat 3. Gravity 4. Momentum 2 people are pulling at opposite ends of a rope. If they are pulling on the rope with equal but opposite forces, what will happen to the rope? 1. It will stay in place between the 2 people. 2. It will move towards the right. 3. It will move towards the left. 4. It will fall to the ground. 2 people are pulling at opposite ends of a rope. The person pulling on the right side of the rope is applying a force of 50N while the person on the left is applying a force of 70N. What will happen to the rope? 1. It will move towards the right. 2. It will move towards the left. 3. It will fall to the ground. 4. It will stay in place. Two dogs are pulling at the same shoe, but the show stays in place. What is happening? 1. One dog is pulling with greater force. 2. Both dogs are pulling with the same force. 3. Both dogs are pulling the shoe in the same direction. When workers spread sand over icy bridges and roads in the winter, how does this help people drive on the roads? 1. The sand increases friction between the road and tires of the car. 2. The sand increases inertia of the car. 3. The sand increases the speed of the car. 4. The sand increases the momentum of the car. 1. Determine the total net force being placed on the rope. 2. Which way will the rope be pulled? Support your answer.