Semester 2 Exam Review

Semester 2 Exam Review Physical Science Chapters 11& 12 Force, Motion, Newton’s Laws

Speed vs. Velocity • Speed is the rate of change of position • Speed = distance time • SI Units: cm/s, m/s, km/h • A scalar quantity (has magnitude, but no direction) • Velocity describes both speed and direction. • Velocity = distance • time • SI Units: cm/s, m/s, km/h • A vector quantity (has magnitude, and direction)

Total distance divided by total time is: • Average speed • Constant speed • Variable speed • Instantaneous speed

Constant Speed • Does not vary • Example?

Constant Speed • Does not vary • Example: CRUISE CONTROL

Instantaneous Speed • The speed at any given ____.

Instantaneous Speed • The speed at any given instant.

A man drives 3 km east from home to the store and then 2 km west to a friend’s house. What is his displacement from his starting point at home? • 1 km west • 1 km east • 5 km west • 5 km east

Acceleration • The rate of change in velocity • a = vf - vi = ∆v tf - ti ∆t

The proper units of acceleration are: • s/km2 • km/h • m/s2 • cm/s

Which of the following is NOT used in calculating acceleration? • initial velocity • average speed • time interval • final velocity

In which of the following conditions does the car NOT accelerate? • A car moves at 80 km/h on a flat, straight highway. • The car slows from 80 km/h to 35 km/h. • The car turns a corner. • The car speeds up from 35 km/h to 80 km/h.

A body accelerates if it_____. • speeds up • slows down • changes direction • all of these

A constant velocity means that acceleration is ____. • positive • negative • increasing • decreasing • constant • zero

Which of the terms below best describe the forces on an object with a net force of zero? • inertia • balanced forces • acceleration • unbalanced forces

Velocity vs. Time graph a. The segments of the graph during which the object is moving at constant velocity are: b. Which segments show positive acceleration? c. Which segments show negative acceleration? d. Where is the greatest acceleration? How do you know?

Velocity vs. Time graph • The segments of the graph during which the object is moving at constant velocity are: BC, DE, FG • b. Which segments show positive acceleration? AB, CD, GH • c. Which segment shows negative acceleration? EF • d. Where is the greatest acceleration? How do you know? DE – steepest slope

The tendency of an object to resist any change in its motion: • Net force • Acceleration • Balanced force • Inertia

Newton’s First Law of Motion • An object in motion stays in motion and an object at rest stays at rest unless acted upon by an unbalanced force. • the resistance of an object to change its motion • also known as the Law of Inertia

Newton’s first law of motion states any of the following EXCEPT: • An object at rest remains at rest unless it experiences an unbalanced force. • An object in motion maintains its velocity unless it experiences an unbalanced force. • An object will tend to maintain its motion unless it experiences an unbalanced force. • An object will tend to maintain its motion unless it experiences a balanced force.

The first law of motion applies to: • only objects that are moving. • only objects that are not moving. • all objects, whether moving or not. • no object, whether moving or not.

Which of the objects has the greatest inertia? • a car parked on the side of the road • a baseball during a pop fly • a computer sitting on a desk • a woman running on a track

An object of large mass has ______ than an object of small mass. • less inertia • more inertia • less weight • greater acceleration

Which answer best describes why a passenger who is not wearing a seat belt will likely hit the windshield in a head-on collision? • forces acting on the windshield • inertia of the unbelted person • acceleration of car • gravity taking over

Newton’s 2nd Law of Motion • A net force causes an object to accelerate in the direction of the net force. • Acceleration = Force mass • a = F/m • m = F/a • F = ma • Units of Force= Newtons (N) or kg▪ m/s2 • Units of Mass = kg • Units of accel. = m/s2

Newton • How is force calculated? • How is weight calculated? • Unit of Force or Weight is ____ or ____

Newton • How is force calculated? F = ma • How is weight calculated? W = mg • Unit of Force or weight is Newton or kg▪ m/s2 So… 1 Newton = kg▪ m/s2

A weightlifter raises a 440-kg barbell with an acceleration of 2.00 m/s2. How much force does the weightlifter exert on the barbell?

A weightlifter raises a 440-kg barbell with an acceleration of 2.00 m/s2. How much force does the weightlifter exert on the barbell? F = ma F = (440 kg)(2.00 m/s2) F = 880 kg▪ m/s2 = 880 N

Friction • Is caused by microwelds that develop between the microscopic bumps on 2 surfaces. • 3 types of friction: static, sliding, and rolling

Acceleration due to Gravity • All objects are attracted to Earth with the same acceleration. • Air resistance exerts an upward force on objects falling through the atmosphere • Terminal velocity - when the force of air resistance equals the force of gravity and the falling object no longer accelerates

The Law of Gravitation • Anything that has mass is attracted by the force of gravity. • Any 2 masses exert an attractive force on each other. • The attractive force depends on the mass of the 2 objects and the distance between them.

4 Basic Forces • Gravity • a long-range force • NEVER disappears • Gravity is the force that gives a galaxy its shape and the universe its structure • Electromagnetic Force • Strong nuclear force • Weak nuclear force

Gravitational Acceleration • Near Earth’s surface, the gravitational attraction of the Earth causes all objects to have an acceleration of 9.8 m/s2 • According to Newton’s 2nd Law, F = ma • F = m x 9.8 m/s2 • The direction of gravitational force is downward • When an object is only under the force of gravity, it is said to be in free-fall.

The gravitational force between two objects depends on_______. • their masses • their velocities • their shapes • the distance between them • more than one of the above (Which ones?)

The gravitational force between two objects depends on_______. • their masses • their velocities • their shapes • the distance between them • more than one of the above

Semester 2 Exam Review