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Forces in Motion Review Chapter 2 How fast? Newton Can you Definitions Pick me! 9.8 m/s/s who? read this? 100 100 100 100 100 200 200 200 200 200 300 300 300 300 300 400 400 400 400 400 500 500 500 500 500 How fast? 9.8 m/s/s for 100? • If the acceleration due to gravity were somehow doubled to 19.6 m/s/s, what would happen to your weight? Your Weight would Double!! How fast? 9.8 m/s/s for 200? • A 12 kg rock falls from rest off a cliff and hits the ground in 1.5 s. • a. Ignoring air resistance, what is the rock’s velocity just before it hits the ground? 14.7 ms/s • b. What is the rock’s weight after it hits the ground? (Hint: Weight is a measure of the gravitational force on an object.) It stays the same How fast? 9.8 m/s/s for 300? • A rock climber dislodges a stone while climbing a mountain. The stone falls straight down, taking exactly 3.5 s to hit the ground. Ignoring air resistance, how fast was the stone traveling when it hit the ground? 9.8 x 3.5= 34.3m/s/s How fast? 9.8 m/s/s for 400? • Which of the following is an example of free fall? • a. a skydiver falling from an airplane • b. a falling or “floating” astronaut in orbit around Earth • c. a ball falling from a rooftop • d. tossing a set of keys to a friend B How fast? 9.8 m/s/s for 500? • A ball is dropped from a rooftop. What is the ball's velocity after 3 s? (Assume that there is no air resistance.) • a. 0 m/s c. 19.6 m/s • b. 9.8 m/s d. 29.4 m/s D Definitions for 100? • Define Terminal Velocity in your own words Definitions for 200? • Define Free Fall in your own words Definitions for 300? • Define inertia in your own words. Which Law is inertia directly related to? Definitions for 400? • Define Newton’s 3rd law of motion. Name three activities/sports that show this law. Definitions for 500? • Mass x Velocity is also known as what??? Pick me for 100? • Explain why results differ on the moon and on Earth when a hammer and a feather are dropped from the same height at exactly the same time. There is no air resistance on the moon acting on the feather They would fall at same rate Pick me for 200? • Newton's third law of motion states that if a force is exerted on an object, another force occurs that • a. is equal in size and opposite in direction. • b. is in the same direction and size. • c. is equal in speed and opposite in direction. • d. is in the same direction and speed. A Pick me for 300? • A golf ball and a bowling ball are moving at the same velocity. Which has more momentum? • a. the golf ball, because it has less mass • b. the bowling ball, because it has more mass • c. They both have the same momentum because they have the same velocity. • d. There is no way to know without additional information. B Pick me for 400? • According to Newton’s first law of motion, a moving object that is not acted on by an unbalanced force will • a. remain in motion. • b. transfer its energy to another object. • c. eventually come to a stop. • d. accelerate in the absence of friction. A Pick me for 500? • Astronauts “fall” or appear to float inside the space shuttle because they • a. are massless. • b. have no gravitational force acting on them. • c. are in free fall. • d. are weightless. C Newton who for 100? • How is inertia related to Newton's first law of motion? It means RESIST CHANGE which is what the 1st law suggests Newton who for 200? • How does Newton's third law explain how a rocket takes off? Equal and opposite forces Rocket’s thrust DOWN Rocket goes UP Newton who for 300? • Explain why friction can make observing Newton’s first law of motion difficult. Friction is always the unbalanced force hear on earth Newton who for 400? • Use Newton’s third law to explain how a person using a hammer to drive a nail into a board is demonstrating conservation of momentum. Action – Swinging Hammer Reaction- Nail moves into wood Momentum is transferred into nail Newton who for 500? • How does Newton's second law explain why it is easier to push a bicycle than to push a car with the same acceleration? The car has much more mass than the bike so it would require much more force Can you read this for 100? • Air resistance is • a. sliding friction. • b. rolling friction. • c. fluid friction. • d. static friction. C Can you read this for 200? • Which of the following games uses conservation of momentum? • a. billiards • b. bowling • c. baseball • d. all of the above Can you read this for 300? • Is it just as hard to catch a thrown bowling ball as it is to throw it? • a. The bowling ball has more inertia while in motion so it's harder to catch it. • b. The bowling ball has the same inertia whether it's standing still or moving, so throwing it and catching it are both equally difficult. • c. The bowling ball has less inertia while in motion, so it's easier to catch than it is to throw. • d. Inertia has nothing to do with how easy or hard it is to throw or catch a bowling ball. It just depends on how strong you are. Can you read this for 400? • The picture below shows a common desk toy. If you pull one ball up and release it, it hits the balls at the bottom and comes to a stop. In the same instant, the ball on the other side swings up and repeats the cycle. How does conservation of momentum explain how this toy works? The total momentum is transferred Into each ball as it moves and stays the Same throughout until friction stops it Can you read this for 500? Daily Double!! • You are a passenger in a car that is moving rapidly down a straight road. As the driver makes a sharp left turn, you are pressed against the right side of the car. Explain why this happens. • The design of a car can make a big difference in its maximum speed. Explain why two cars that have the same mass and are powered by the same type of engine might be able to reach very different speeds on the same road. Final Question Distance fallen during this Time (s) Velocity m/s second 0 0 0 1 v = 1 × 9.8 = 9.8 4.9 2 v = 2 × 9.8 = 19.6 4.9 + 9.8 = 14.7 3 ? 4.9 + 9.8 + 9.8 = 24.5 4 ? 4.9 + 3(9.8) = 34.3 5 ? ? 6 ? ? 7 ? ? Final Question Distance fallen during this Time (s) Velocity m/s second 0 0 0 1 v = 1 × 9.8 = 9.8 4.9 2 v = 2 × 9.8 = 19.6 4.9 + 9.8 = 14.7 3 3 x 9.8 = 29.4 4.9 + 9.8 + 9.8 = 24.5 4 4 x 9.8= 39.2 4.9 + 3(9.8) = 34.3 5 5 x 9.8 = 49 4.9 + 4(9.8) = 44.1 6 6 x 9.8 = 58.8 4.9 + 5(9.8) = 53.9 7 7 x 9.8 = 68.6 4.9 + 6(9.8) = 63.7
"Forces in Motion Review"