Name Date P Lesson 4 Forces and Simple Machines

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1 Lesson 4 Forces and Simple Machines OAA Science Lesson 4 40

2 Lesson 4: Forces and Simple Machines Student s Reference Sheet: 6 Simple Machines: Screw - Swivel Stool - Spiral Stair Case - Inclined Plane - Slide - Hill - Pulley - Stage Curtains - Crane - Wedge - Axe - Knife - Wheel and axle - Door Knob - Wagon - Lever - Toilet Handel - Hammer - Forces: Friction- the force that resists relative motion between two bodies in contact Gravity- the gravitational attraction or force of one mass body to another Inertia- the tendency of an object to resist a change in motion (straight line /the force that wants to continue a body in the path it is already traveling until another forces acts on it) ex: gravity and inertia = orbit paths Force- is a push or pull in a particular direction. Forces affect how objects move. They may cause motion; they may also slow, stop, or change the direction of motion of an object that is already moving. Forces can affect motion in several ways: They can make objects start moving They can make objects move faster They can make objects move slower They can make objects stop moving They can make objects change direction OAA Science Lesson 4 41

3 Balanced Forces- Two or more opposite forces are balanced forces if their effects cancel each other and they do not cause a change in an object's motion. If two forces of equal strength act on an object in opposite directions, the forces will cancel, resulting in a net force of zero and no movement. Unbalanced Forces: If the effects of the forces don't cancel each other, if one force is stronger than others, the forces are unbalanced forces. Unbalanced forces cause a change in motion; speed and/or direction. Energy: Kinetic and Potential How to find PE: PE= mass x gravity (9.8) x height The key is locating the highest PE is to determine where an object is at it s HIGHEST location. The LOWEST location would be lowest PE. How to find KE: KE= mass x speed x speed x 0.5 The key to locating the highest KE is to determine where an object is MOVING THE FASTEST. The lowest KE location would be its SLOWEST SPEED. Use these symbols: Highest PE Lowest PE Highest KE Lowest KE Speed = Distance/Time OAA Science Lesson 4 42

4 Student Practice: Simple Machines 1. Students want to plant flowers into the ground for a community service project at school. Which of these tips on a garden tool would take the least force to dig a hole in the ground? OAA Science Lesson 4 43

5 2. Which of the following simple machine is a wedge? a. Wheel barrel b. Deliver Truck c. Axe d. Flag Pole 3. Which simple machine is made up of an inclined plane wrapped around a bar? a. Wedge b. Wheel and axle c. Screw d. Pulley 4. An adult and a small child are at the playground. The child sits on the end of a seesaw, as shown. The adult weighs twice as much as the child. At which point on the seesaw will the adult need to sit in order to balance the child s weight? A. point A B. point B C. point C D. point D OAA Science Lesson 4 44

6 Use the information below to answer questions 5 and 6. Block and Ramp Students investigated the motion of wooden blocks on ramps. They used two boards, each two meters long, to create ramps. They set the ramps up at different heights, as shown in the diagram below. Next they took two identical blocks (I and II) and placed one at the top of each ramp. They placed the blocks so that the back edge of each block was even with the edge of the ramp (distance = 0 meters). The students held the blocks so that the blocks would not slide until the students released them. The students released the blocks at time = 0 seconds. They measured the total distance traveled by each block at 1-second intervals as the blocks slid down the ramps. The students recorded their results as shown below.40 8; OAA Science Lesson 4 45

7 5. Which conclusion is supported by the results of this investigation as expressed in the data table? A. As the travel time increases, the speed of the block decreases. B. As the ramp steepness is increased, the travel time of the block increases. C. As the distance traveled increases, the average speed of the block increases. D. As the height of the ramp is increased, the average speed of the block decreases. 6. In your Answer Document, name two forces that acted on the blocks as they slid down the ramps. Describe or show how each force you listed affected the motion of the block. (4 pts) OAA Science Lesson 4 46

8 Use the information below to answer questions 7 10 Toy Car Race Ms. Williams science class uses a toy car race to study and collect data about forces and motion. The racetrack shown has a 6-meter ramp and a 5-meter level section to the finish line. Two cars compete at a time. The data table and graph below show the speed and total distance traveled for car 1 and car 2 during the first three seconds of a race. OAA Science Lesson 4 47

9 7. On what section of the racetrack will the forces on the cars be balanced? A. the starting block B. the ramp only C. the level section after the ramp D. the entire track 8. At what point on the track does a car reach its fastest speed? A. halfway down the ramp B. at the bottom of the ramp C. halfway down the level section D. at the finish line 9. The data table and graph show speeds and distances during a race between car 1 and car 2. In your Answer Document, state which car won the race. Provide support to explain why your answer is correct. (2 points) OAA Science Lesson 4 48

10 10. In the diagrams below, g is the force of gravity, r is the force of the ramp acting on the car and f is the force of friction. Which diagram shows the directions of the forces acting on a car as it travels down the ramp? OAA Science Lesson 4 49

11 11. In your Answer Document, identify two forces that act on a wheel chair while going down a ramp? Describe or show how each force you listed affected the motion of the wheel chair. (4 pts) OAA Science Lesson 4 50

12 Use the information below to answer questions 12 and 13. Motion Diagram The graph below shows the position of a car in motion along an east-west road over a period of 10 minutes. The car s position is recorded at 1-minute intervals. At time = 0, the car s position is at the starting point. 12) What is the car s motion relative to the starting point at time = 8 minutes? A. at rest at the starting point B. in motion at the starting point C. moving toward the starting point D. moving away from the starting point 13) What is the total distance traveled by the car after 10 minutes? A. 600 meters B. 1,200 meters C. 2,000 meters D. 3,600 meters OAA Science Lesson 4 51