Science Test Ch. 12
What is Newton's second law?
Acceleration is produced when a force acts on a mass. The greater the mass (of the object being accelerated) the greater the amount of force needed (to accelerate the object).
Projectile motion has a horizontal component.
After you have thrown a ball, no horizontal forces are acting on the ball (if air resistance is ignored). So, the horizontal component of velocity of the ball is constant after the ball leaves your hand.
Why do objects fall to the ground when dropped?
All objects in the universe attract each other through the force of gravity.
What is Newton's first law?
An object at rest will remain at rest unless acted on by an unbalanced force. An object in motion continues in motion with the same speed and in the same direction unless acted upon by an unbalanced force.
What is an example of equal forces?
Example: The action force of Earth pulling on an object and causing it to fall is much more obvious than the equal and opposite reaction force of the falling object pulling on Earth.
Zookeepers lift a stretcher that holds a sedated lion. The total mass of the lion and stretcher is 175 kg, and the upward acceleration of the lion and stretcher is 0.657 m/s2. What force is needed to produce this acceleration of the lion and the stretcher?
F = 175 kg × 0.657 m/s2 F = 115 kg × m/s2 F = 115 N
What is the relationship between free-fall acceleration and mass?
In the absence of air resistance, all objects falling near Earth's surface accelerate at the same rate regardless of their mass.
What determines how much an object speeds up or slows down?
Net force is equal to mass times acceleration. The unbalanced force on an object determines how much an object speeds up or slows down.
What makes an object speed up, slow down, or change directions?
Objects change their state of motion only when a net force is applied.
Why does a projectile follow a curved path?
Projectile motion has two components—horizontal and vertical. When the two motions are combined, they form a curved path.
What is a example of inertia?
Seat belts and car seats provide protection. When a car comes to a stop, your seat belt and the friction between you and the seat provide the unbalanced backward force that is needed to bring you to a stop as the car stops.
Newton's second law can also be stated as...
The acceleration of an object is proportional to the net force on the object and inversely proportional to the object's mass. a=f/m
What is the total momentum after objects collide?
The total momentum of two or more objects after a collision is the same as it was before the collision. In other words, the total amount of momentum in an isolated system is conserved. This principle is the law of conservation of momentum.
How are weight and mass related?
Weight is equal to mass times free-fall acceleration.
What happens when an object exerts a force on another object?
When one object exerts a force on a second object, the second object exerts a force equal in size and opposite in direction on the first object. This is Newton's third law.
Projectile motion also has a vertical component.
When you throw a ball, gravity pulls it downward, which gives the ball vertical motion. In the absence of air resistance, gravity on Earth pulls objects that are in projectile motion downward with an acceleration of 9.8 m/s2, just as it pulls down all falling objects.
For equal masses...
a greater force produces a greater acceleration.
For equal forces...
a larger mass accelerates less.
mass =
a measure of the amount of matter in an object
Forces in a force pair do not...
act on the same object.
gravity is acting on the...
body
Force is related to...
change in momentum.
Gravitational force...
decreases as distance increases.
Equal forces don't always have...
equal effects
What is Newton's third law?
for every action there, there is an equal and opposite reaction
What is the equation for Newton's second law?
force = mass × acceleration (or) F = ma
Astronauts in orbit are in...
free fall
Two objects, whether large or small, always have a...
gravitational force between them. When something is very large, like Earth, the force is easy to detect.
All matter is affected by...
gravity
Projectile motion has a...
horizontal component
Weight is measured...
in newtons.
Forces always occur...
in pairs.
Momentum and velocity are...
in the same direction
Gravitational force...
increases as mass increases.
Force
is measured in newtons (N): 1 N = 1 kg × 1 m/s2
What are the SI units of momentum?
kilograms times meters per second (kg•m/s).
Weight is different from...
mass
Momentum increases as...
mass and velocity increase
What is the equation for weight?
mass x free-fall acceleration (or) w = mg
weight
measure of the gravitational force exerted on an object
How do you calculate the momentum of an object?
momentum = mass x velocity, or p = mv
Calculate the momentum of a 6.00 kg bowling ball moving at 10.0 m/s down the alley toward the pins.
p = mv = 6.00 kg × 10.0 m/s p = 60.0 kg • m/s (toward the pins)
momentum
quantity defined as the product of the mass and velocity of an object
Objects tend to maintain their...
state of motion
terminal velocity
the constant velocity of a falling object when the force of air resistance is equal in magnitude and opposite in direction to the force of gravity
projectile motion
the curved path that an object follows when thrown, launched, or otherwise projected near the surface of Earth
weight =
the gravitational force an object experiences because of its mass
free fall
the motion of a body when only the force of
inertia
the tendency of an object to resist a change in motion unless an outside force acts on the object (resistance to change)
Projectile motion also has a...
vertical component
Air resistance can balance...
weight.