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Chapter 4 and 5 Test
Terms in this set (68)
a force that comes from gravity pulling down on any object with mass.
the English unit of force equal to 4.448 newtons.
the metric unit of force, equal to the force needed to make a 1 kg object accelerate at 1 m/s2.
a pulling force that acts in a rope, string, or other object.
a squeezing force that can act on a spring.
a force that always resists motion. The force two objects exert on each other when they make contact.
the friction force that resists the motion of an object moving across a surface.
the friction force that resists the motion between two surfaces that are not moving. Motionless; greater than kinetic force
the sum of all forces acting on an object.
combined forces that result in a zero net force on an object.
the state in which the net force on an object is zero. NOT accelerating
the force that a surface exerts on an object that is pressing on it. Is always perpendicular to the surface
a diagram showing all the forces acting on an object.
Newton's first law
an object at rest will stay at rest and an object in motion will stay in motion with the same velocity unless acted on by an unbalanced force.
result in a net force on an object that can cause changes in motion.
the property of an object that resists changes in its motion.
Newton's second law
acceleration is force divided by mass.
Newton's third law
for every action force there is a reaction force equal in strength and opposite in direction.
A push or a pull
Likes repel and opposites attract
Weakest force; cumulative
Strong nuclear force
Strongest force; holds nuclei together
Weak nuclear foece
Holds protons and neutrons together
The amount of matter in an object; does not change with different gravitational pulls; measured in grams/kilograms
Weight=mass times strength of gravity
Friction Rolling on an object
Three situations in which force is created
Muscles, moving matter (wind), massive objects (planets)
What are the units of force
Newtons and pounds
Does the MASS of an object change if the object is moved from one planet to another?
No because gravity only affects weight.
What does it means if the strength of gravity is 9.8 N per kg?
Each kg of mass weighs 9.8 N
What are devices or inventions designed to DECREASE friction?
Oil, ball bearings, magnetic levitation, water
What are five devices or inventions designed to INCREASE friction?
Tires, nails,cleated shoes, wood, rubber
If the force squeezing two surfaces together is DECREASED, the force of friction between the two surfaces will most likely what?
T or F: a well oiled machine has no friction
False; a super conductor is a machine that has no friction
What is the difference between static friction and sliding friction?
Static friction occurs at rest and sliding friction occurs in motion
T or F: friction makes energy vanish.
False; friction changes motion energy into heat, sound, or light
A vector is an example of a physical quantity that:
Includes information about quantity and direction
If an object is in equilibrium, it means:
The net force on the object is zero
If a force has a negative value, such as -100 N, that means the force:
Acts in the opposite direction from a +100 N force
A child weighing 200 N is sitting on a swing. The swing is supported by two ropes, one on each side. What is the tension in one of the ropes?
Name a force and describe two changes it makes.
Electromagnetic acts between proton and neutron charges and it holds atoms together to make molecules.
What information do you need to describe a force?
Size and direction
What happens to a springs force if you stretch it more?
Its force increases
How does the strength of gravity affect the mass and weight of objects measured on earth and the moon?
When gravity it weaker, it weighs less.
How are force vectors represented?
Does it require more force to start an objects sliding or to keep it sliding?
Explain why ice generally has very little friction when it is in contact with other materials.
Because friction depends on the force between the surfaces
Name two types of energy generated by friction and give an example of each
Heat -rubbing hands together; light- fire
Why is it much easier to slide a cardboard box when it is empty compared to when it is full of heavy books
Because the friction is increased when it has less mass
Standing on earth gravity exerts a downward force on you. What other force acts on you? What is the direction of the other force? What do you m know about the magnitude (strength) of this other force?
Normal force; it is opposite of gravity; normal F =gravity
If the net force on an object is zero, can the object be moving?
Yes, in some cases, an object moving at a constant speed In a straight line would be in equilibrium.
What four main forces act on an airplane in flight? If the plane accelerates forward, Which two forces must be out of balance? To fly on a level path, Which two forces must be in balance?
Drag (air resistance), lift, thrust, and weight. Drag and thrust. weight and lift
You and your friend pull on opposite ends of a rope, each eirh a force of 10 N. What is the tension in the rope?
Newtons first law
Law of inertia; the motion of an object will remain unchanged unless acted upon by an outside force (direction and velocity stays constant)
Newtons second law
Force=mass times acceleration; a=f/m; m=f/a. A creation is directly proportional to force. Acceleration is inversely proportional to mass.
F(change in t) = m (chance in v)
A conserved quality that cannot be created or destroyed and just changes forms; momentum=mass times velocity; mass times change in v= change in momentum
Newtons third law
For every reaction, there is an equal and opposite reaction; the forces are the same; less mass=more acceleration
What creates the force of a flag flapping back and forth
What creates the force of a soccer ball being passed
What causes the force of a hail falling to the ground
What causes a tide going from high to low
What does unbalanced force cause
What force makes you move forward on a skateboard
The ground pushing on you
Why do action reaction forces result in zero net froce
Because they are acting on different objects
What pushes a jet forward
The fuel sends it forward
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