Honors FORCE Study Guide KEY

Transcription

1 Honors FORCE Study Guide KEY Answer the following questions for each objective in your notebook: Objective 1: Students will know the different types of forces and how they affect the movement of objects. (Includes: gravity, friction, contact, air resistance, centripetal, balanced and unbalanced) 1. What is the definition of a contact force? A force between objects touching each other 2. What is the definition of gravity? The force that objects exert on each other because of their mass 3. What is the definition of friction? A force that resists the motion between two surfaces in contact 4. What is the definition of air resistance? The force between air and an object moving through air. 5. What is the definition of centripetal force? A force that causes an object to move in a curved or circular path. 6. What is a net force? The overall force acting on an object when all of the forces acting on it are combined. A hang glider is an unpowered flying apparatus for a single person, consisting of a frame with a fabric airfoil stretched over it. 7. Draw a picture of yourself hang gliding (stick figures are ok). Label all the forces acting on your body (include arrows). gravity air resistance 8. If the air resistance acting on you is 600 N and the force of gravity is equal to 1400 N when you initially jump out of the plane, what is the net force acting on you? 800 N 9. Are the above forces balanced or unbalanced? unbalanced

2 10. How can the motion of an object be determined by balanced or unbalanced forces? There is no motion when the forces acting on an object are balanced and there is motion in the direction of the applied force when the forces acting on an object are unbalanced. 11. After you have been sailing through the air for a while, the force of air resistance is now 1400N and the force of gravity is 1400N what is it called when an object is continuing to fall but the forces acting on the object are equal to each other; the object is no longer accelerating? Flyer has reached terminal velocity 12. You are pushing a wheel barrow around the yard. Draw arrows and label them with contact force, friction, and gravity acting on the wheel barrow. Gravity Air Resistance Contact Force Friction 13. In a game of tug-of-war, you pull on the rope with a force of 75N to the right and your friend pulls on the rope with a force of 100N to the left. What is the net force on the rope? 25N 14. Two dogs are pushing on a box; one with a force of 280N to the right and another dog is pushing on the box with a force of 280N to the right. What is the net force on the box? 0 N 15. Two dogs are pushing on a box; one with a force of 15N to the right and another dog is pushing on the box with a force of 10N to the right. What is the net force on the box? 25 N 16. Two kids are pushing on the lid of their sandbox; one with a force of 8N to the right and the other with a force of 4N to the right. What is the net force on the lid of the sandbox? 12 N 17. Explain the difference between balanced and unbalanced forces. Balanced Forces are equal in size and opposite in direction they do not cause the motion of an object. Unbalanced forces are either different sizes or in the same direction they do cause a change in an object s motion. 18. What happens to the object s motion when balanced forces are applied to it? The object does not move. 19. What happens to the object s motion when unbalanced forces are applied to it? The object moves in the direction of the force.

3 20. Draw a diagram of a ping pong game. List the forces that act on a Ping-Pong ball during a game and explain how each force affects the motion of the Ping-Pong ball. Air Resistance Gravity Contact Force Friction occurs between the paddle and the ball and the ball and the table slowing down the motion of the ball. Gravity makes the ball fall back down to the table after it is hit, centripetal force also causes the ball to move in a curved path, contact force acts on the ball when the paddle hits it and contact force happens when the ball hits the table, friction occurs between the ball and table and the ball and the paddle. 21. Draw a diagram of a golf ball during a round of golf. List the forces that act on a golf ball during a round of golf and explain how each force affects the golf ball. Air Resistance Contact Force Gravity Gravity pulls the ball back down to the ground, centripetal force causes the ball to move in a curved path, friction slows the ball down while in the air (air resistance) and on the ground when it is rolling on the grass, a contact force is present when the golfer hits the ball with the club.

4 Objective 2: Students will be able to understand and describe inertia of an object according to Newton s First Law of Motion. 1. Which has more inertia? (Circle one): - A kid riding his tricycle - A train traveling at its fastest speed - A soccer ball being kicked by David Beckham. 2. You are skateboarding down the new bike path listening to your ipod. You are not paying attention and hit a boulder that is in the middle of the path. Explain using Newton s First Law of Motion what happens to both you and the skateboard. The skateboarder will stop because the boulder will be in the way but your body will continue to move in the same direction as it was moving until something stops you (like the pavement ouch!) 3. Why do we often call Newton s First Law of Motion the Law of Inertia? Inertia is the resistance of motion and according to Newton s first law of motion an object will maintain its motion (resist a change in motion) unless a force is applied to it. 4. What happens when you apply a force to an object at rest? You change the motion of the object it will move. 5. How does friction (air resistance) affect the motion of an object? Friction opposes motion prevents it. 6. Explain what happens when a person wears a seat belt and when he or she does not. For both cases, describe the direction objects inside the car move whenever the car s velocity changes. (Be specific and include a diagram.) When a person wears a seatbelt they become one with the car and their motion will be the same as the car s motion. Without a seatbelt a person will continue to move if a car stops unless a force (like the windshield ouch!) stops it. 7. How does Newton s First Law of Motion explain question 6 above? This occurs because Newton s First Law of Motion states that an object in motion will stay in motion unless a net force acts on it.

5 Objective 3: Students will be able to calculate force, mass and acceleration according to Newton s Second Law of Motion. 1. What is the definition of a force? A push or pull; something that changes the motion of an object. 2. What is the definition of mass? A measure of how much matter an object is made of. 3. What is the definition of acceleration? The rate at which velocity changes over time. 4. What is an objec t acceleration if it is falling though air towards Earth? 9.8m/s 2 5. You are pushing two boxes across the floor with the same amount of force. One box is more massive than the other. What happens to the acceleration the more massive box? decreases 6. Two students are moving a cart of science supplies for the ninth grade science teachers. The full cart has a mass of 55kg. The frictional force between the cart and the floor is.8n to the left. One student is pushing the cart with a force of 10N to the right and the other is pulling with a force of 18N to the right. a. What is the net force acting on the cart? 27.2 N b. What is the acceleration of the cart?.49 m/s 2 c. If the mass of the cart is doubled but the force on it remained constant, what would happen to the acceleration of the cart? decrease by half d. If you increase the force on an object what happens to the acceleration? Increases e. If you increase the mass of an object, what happens to the acceleration? decreases 7. If you push a tennis ball and a ping pong ball with the same force, which one would have great acceleration? Ping-pong ball less mass 8. A quarterback throws a football at an acceleration of 8 m/s 2. The mass of the football is 12 kg. What force did the quarterback throw that ball at? 96 N 9. A 400 N force acts on a 5 kg object. What is the acceleration of the object? 80 m/s John throws a stack of shingles off of the roof of his house into the dumpster below. What is the stack s mass if John tosses it off the roof with a force of 22N? 2.24 kg 11. Jack tosses a hammer down to his coworker from on top of his ladder. What is the hammer s mass if Jack tosses it with a force of 2N?.2 kg 12. What mass does a rain drop have if it is faling towards the ground and hits the ground with a force of.002 N? kg 13. Using Newton s second law of motion - how does the mass of an object affect its acceleration? More mass = decrease in acceleration or less mass = greater acceleration (when the force is the same) 14. Using Newton s second law of motion, how does the force applied to an object affect the object s acceleration? Increase force = increase in acceleration or decrease force = decrease acceleration

6 Objective 4: Students will be able to understand that for every action there is an equal and opposite reaction per Newton s Third Law of Motion 1. Identify the action/reaction force pair involved when you jump on a trampoline. Action Force = you jumping on the trampoline Reaction Force = the trampoline pushing back on you 2. Identify the action/reaction force pair involved when you catch a ball. Action Force = ball hitting oyur glove Reaction Force = you pushing back n the ball 3. How are balanced forces different from action reaction forces? Balanced forces act on the same object and Action-Reaction forces act on different objects. 4. If the action force is 10 N, what is the reaction force? 10 N 5. If the action force is being applied to the right what direction is the reaction force? To the left 6. Action reaction forces are equal in size and opposite in direction. 7. You Jump on the legs of a pogo stick. The action force is your weight pushing down on the legs of the pogo stick. What is the reaction force? Pogo stick pushing back up on you or the ground pushing up on the pogo stick