Physical Science State Assessment Review S.HS.2B.1.1

Newton’s First Law of Motion (law of inertia) – an object in motion stays in motion at a constant velocity and an object at rest stays at rest unless acted upon by an outside force This outside force is usually friction.

friction – a force that acts between two materials that are in contact with each other as they move past one another The more smooth a surface is, the less friction it applies. Only when friction is present do we need a force to keep the object moving. Without friction a moving object would never stop.

Types of friction: sliding friction – when two surfaces slide past each other rolling friction – when a round object rolls over a flat surface fluid friction – friction between a fluid (any liquid or gas) and the surface of an object Air resistance is a type of fluid friction.

Air Resistance: All objects, regardless of their size or mass, accelerate toward the surface of the Earth at a rate of 9.8 m/s/s. Gravity is the force that causes this acceleration. As objects fall they experience friction with the air (fluid friction). This air resistance is a force that acts in the opposite direction of gravity.

terminal velocity - – the point at which a falling object stops accelerating because the force of air resistance becomes equal to the force of gravity

Questions 1. An object is pushed with a force and begins to move across a frictionless surface. Which best describes the object’s motion after the force stops acting? A. constant velocity B. increasing velocity C. variable acceleration D. decreasing acceleration

Questions 1. An object is pushed with a force and begins to move across a frictionless surface. Which best describes the object’s motion after the force stops acting? A. constant velocity – correct answer B. increasing velocity C. variable acceleration D. decreasing acceleration

2. An object is pushed with a force and experiences friction. Which best describes the motion of this object after the force stops acting? A. constant velocity B. increasing velocity C. variable acceleration D. decreasing velocity

2. An object is pushed with a force and experiences friction. Which best describes the motion of this object after the force stops acting? A. constant velocity B. increasing velocity C. variable acceleration D. decreasing velocity – correct answer

3. Which of the following statements best describes air resistance? A. The rolling friction experienced between an object and the air. B. A force of gravity. C. The fluid friction experienced between an object and the air as the object falls. D. The sliding friction experienced between an object and the air.

3. Which of the following statements best describes air resistance? A. The rolling friction experienced between an object and the air. B. A force of gravity. C. The fluid friction experienced between an object and the air as the object falls. – correct answer D. The sliding friction experienced between an object and the air.

4. Choose the surface or substance that would apply the greatest amount of friction. A. air B. a tile floor C. a carpeted floor D. motor oil

4. Choose the surface or substance that would apply the greatest amount of friction. A. air B. a tile floor C. a carpeted floor – correct answer D. motor oil