Transcript Newton2and3
Newton’s Second Law of Motion Mrs. Anna Ward James Martin MS Do Now!!! Draw the following in your science notebook… FORCE = MASS times ACCELERATION FORCE = 1000 x .05 FORCE = 50 NEWTONS Announcements Test on Newton’s Laws on Friday Notebook Check next Friday Agenda Individual Mini Labs at our desk on Newton’s Second Law Guided Notes on Newton’s Second Law (F=ma) Partner Mini-Lab on Newton’s Third Law Guided Notes on Newton’s Third Law Video on Newton’s Laws How are force and acceleration related? 1. Directions: Tie a paper clip to each end of the yarn. 2. Hold the single paper clip in the middle of your desk; hang the other end of the yarn over the edge. Let go and observe. 3. Add one more paper clip to the hanging end and repeat the experiment. Observe what happens. 4. Repeat step #3. Questions for your notebook: Questions: 1. What happened each time that you let go of the yarn? 2. Explain the relationship between the number of hanging paper clips and the motion of the paper clip on the table. Newton’s Second Law Newton’s Second Law states that the acceleration of an object increases with increased force and decreases with with increased mass. In simple terms… Force, mass, and acceleration have a relationship http://www.d123.org/olhms/ebarlos/documents/PSC0 2BAD.pdf Newton’s 2nd law We describe this relationship using the formula: F=ma or Force=mass x acceleration Newton’s Second Law Force is measured as mass with acceleration, so… Kg/m/s2 Which is also known as a NEWTON 1 Kg/m/s2 = 1 Newton or 1 N Newton’s 2nd Law—Apply the Knowledge What force is needed to accelerate a 10 kg shopping cart 3 m/s2? What do you know? What do you want to find out? Write the formula: Substitute into the formula: Calculate & Simplify: Check that your units agree Answer: F=30 N CFU What force is needed to accelerate a 20 kg boulder to 2 m/s2? What do you know? What do you want to find out? Write the formula: Substitute into the formula: Calculate & Simplify: Check that your units agree Answer: F=40 N CFU If a force of 35N is added to a box and it accelerates to a rate of 7 m/s2, what is the mass of the box? What do you know? What do you want to find out? Write the formula: Substitute into the formula: Calculate & Simplify: Check that your units agree Answer: mass=5 kg Independent Practice F=ma 1. What net force is required to accelerate a car at a rate of 2 m/s2 if the car has a mass of 3,000 kg? 2. A 10 kg bowling ball would require what force to accelerate down an alleyway at a rate of 3 m/s2? 3. Victor has a car that accelerates at 5 m/s2. If the car has a mass of 1000 kg, how much force does the car produce? Newton’s Third Law: Investigation 1. With a partner, hook the two spring scales together. 2. Pull gently on your spring scale while your partner holds but does not pull on the other side. 3. Observe and record the amount of force that is shown on your scale and on your partner’s scale. 4. Both of you pull together. Observe the forces shown on each side. Investigation Questions: 1. What happened to your partner’s force as your force increased? 2. What happened when you both pulled? 3. Explain why you think what you observed in each case happened. 4. Can you think of a way to use the scales to show Newton’s first or second law? Newton’s Third Law Newton’s Third Law states that every time one object exerts a force on another object, the second object exerts a force that is equal in size and opposite in direction back on the first object. Newton’s Third Law—in more simple terms Sometimes referred to as law of “EQUAL and OPPOSITE” For every reaction, there is an “equal and opposite” reaction What ever happens, there is an exact (but opposite) force that happens as well. CFU… So if Nixon pushes against a wall with a force of 25N, how much force does the wall exert on him, and in what direction? Action-Reaction Pairs The force that is exerted on an object and the force that exerts back are known as action-reaction pairs. Example: When Abed bangs his toe into the leg of the table, the same amount of force he exerts on the table is exerted back on his toe. Action-Reaction Pairs http://www.d123.org/olhms/dedie/d ocuments/2-3Forces.pdf Brainstorm… What are some other examples of Action/Reaction Pairs? CFUs What are the action reaction pairs with: Jumping? Walking? Catching a Ball? Larkam’s bat hitting a baseball? The door shutting? Asia’s book bag hitting the floor? Video… http://www.youtube.com/wa tch?v=2OJjbztWitk EXIT TICKET Suppose Robert is holding a basketball while standing still on a skateboard. Justin and the skateboard have a mass of 50kg. He throws the basketball with a force of 10N. What is his acceleration before and after he throws the ball?