Forces and their affect on motion
Fundamental forces and their influence
1.3.1. Analyze the forces acting on objects.
Describe how machines transform forces (e.g., a long lever allows a small downward input force to be transformed into a large upward output force). Describe the strength (in newtons [N]) and direction of forces acting on an object. Measure and describe the sum of all the forces acting on an object. Describe how forces between objects occur, both when the objects are touching and when the objects are apart. Explain that the strength of a gravitational force between two objects depends on the mass of the objects and the distance between the objects.
1.3.2. Analyze the effects of balanced and unbalanced forces on the motion of an object.
Describe the balanced forces acting on an object moving at a constant speed along a straight line, 1st Law of Motion (e.g., a car traveling at a constant speed of 60 mph on a straight freeway has a force pushing it forward balanced by frictional forces acting in the opposite direction). Explain how unbalanced forces change the speed and/or direction of motion of different objects moving along a straight line, 2nd Law of Motion (e.g., a 2-kg object needs twice the unbalanced force to speed up the same amount as a 1-kg object). Investigate and describe that forces always come in pairs, 3rd Law of Motion (e.g., pull a spring scale against another spring scale, as water blasts out of a bottle rocket two forces act - a force on the water and an equal force on the rocket).
1.1.2. Apply an understanding of direction, speed, and acceleration when describing the linear motion of objects.
Describe the linear motion (speed, direction, and acceleration) of an object over a given time interval relative to Earth or some other object (e.g., as a car accelerates onto a freeway the car speeds up from 30 km/hr to 90 km/hr in 10 sec.).
Determine and explain the average speed of an object over a given time interval when the object is moving in a straight line.e]