Work occurs wherever something is moved and an obect is put in motion. The motion of an object is described with three things: position, direction and speed. Forces come into play with work because they push and pull objects. All forces have size and direction. Some, like the pull of gravity toward a black hole, are immense, while others, like the push of an ant on a breadcrumb, are very small.
Work is possible because all objects have mechanical energy, including potential (energy based on position) and kinetic (energy of motion) energy. Mechanical energy is transferred from one object to another by pushing or pulling it. How fast these objects move depends on the position they began in and how much force was applied to them.
Which of the following is an example of a situation where work occurs?
A a glass of water sitting on the counter
B a leaf resting on a rock
C a student sitting at a desk
D a baseball soaring through the air
The position of an object is its location relative toa second or background object, which becomes the reference point. We describe positions using terms like on top, next to, to the right of or just north of.
An object's motion is measured by its speed and direction from the reference point. Since no objects are truly "still" or completely motionless, motion is always relative to some other, usualy larger, object or reference point.
A over there
B on the table
C right there
Speed is the rate at which an object moves relative to its reference point. Average speed is the total distance divided by the total time. We use average speed because the speed of an object may very over time. Common measures of speed include miles per hour, meters per second or kilometers per minute. If you drive at a speed limit of 65 miles per hour, it means that in one hour you will have traveled 65 miles from the reference point of where you began.
Because the speed at which an object travels over time,
A it is impossible to calculate any type of speed measurement.
B distance is considered the more important measurement.
C average speed is used which is total distance divided by total time.
D tune us considered the more important measurement.
Sir Isaac Newton's law govern force and motion. The Third Law of Motion says that whenever you exerts an equal and opposite force on you. Or, for every action there is an equal and opposite reaction. For example, when you jump off the ground, there is a downward push of your legs into the ground as well as the upward push of your body into the air.
A While sitting in a chair, you exert force on the chair, and the chair exerts the same amount of force back on you.
B A basketball sitting on the court doesn't move until something pushes it.
Potential energy is based on an object's ________________________.
The energy of motion is called ___________________ energy
A force that opposes motion between two touching surfaces is called:
The rate an object is moving relative to a reference point is its
C deceleration rate
D mechanical potential energy rate
The speed at which an object is moving in a specific direction is its
B acceleration rate
D mechanical potential energy rate
An object's average speed is found by dividing the total distance the object tavels by the total
A mass of the object
B acceleration of the object
C specific gravity of the object
D time it takes to move that distance
Newton's First Law of Motion states that an object in motion tends to stay in motion unless
A starts to decelerate
B runs out of kinetic energy
C is acted upon by another force.
D approaches the speed of light
Newton's Second Law of Motion says that the acceleration of an object depends on the object's mass and the
A equation E = MC2
B amount of force applied to the object.
C negative acceleration factor
D amount of atoms the object has
Newton's Third Law of Motion states that for every action there is an equal and opposite reaction. Which of these illustrates Newton's Third Law?
A Two students of similar mass run into each other. They bounce off each other when they collide.
B Two students of similar mass run side by side into a wall and punch holes of equal size before emerging on the other side.
C Two students of similar mass run in opposite directions, but one accelerates at twice the rate of the other.
D Two students of similar mass run at the same speed in opposite directions on a track. They will collide with 400 Newtons of force in 400 meters.
Which device makes work easier? Why? Explain.
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