Download ch 12 review answers

.ch 12 review answers
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1. The property of matter that resists changes in motion is called inertia
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What kind of friction occurs as a fish swims through water? Fluid friction
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3.
The product of an object’s mass and velocity is its momentum
4. Which universal force acts only on the protons and neutrons in a nucleus? Strong nuclear
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What force is responsible for the repulsion between two positively-charged particles?
electromagnetic
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6.
Newton’s third law of motion describes action reaction
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7.
The gravitational force between two objects increases as mass increases
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8.
The SI unit of force is the Newton
9. If a force of 12 N is applied to an object with a mass of 2 kg, the object will accelerate at 6 m/s/s
____ 10.
The acceleration due to gravity on the surface of Mars is about one third the acceleration due
to gravity on Earth’s surface. The weight of a space probe on the surface of Mars is about 1/3
____ 12.
As you push a cereal box across a tabletop, the sliding friction acting on the cereal box
stays the same as long as you don’t stop or start it
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13.
The forces acting on a falling leaf are gravity and fluid friction
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14.
When a pair of balanced forces acts on an object, the net force that results is zero
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15.
When an unbalanced force acts on an object, a change in motion occurs
____ 17.
What is conserved when two objects collide in a closed system?
Momentum, energy
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19.
Projectile motion is caused by gravity acting on a launched object
____ 20.
An orange might roll off your cafeteria tray when you stop
suddenly because of inertia
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21.
The force that keeps an object moving in a circle is called centripetal force
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attract
When opposite poles of two magnets are brought together, the poles
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23.
Which of the four universal forces is the weakest? gravity
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24.
Your weight equals your mass times gravity
gravity
____ 25. An open parachute increases air resistance of a falling sky diver by
increasing surface area or fluid friction
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According to Newton’s second law of motion, the acceleration of an object equals the net
force acting on the object divided by the object’s mass
____ 27.
With which of the following is the weak nuclear force associated?
Nucleus of the atom
28. A tow truck exerts a net horizontal force of 550 N on an 710-kilogram car. What is the acceleration of the car
during this time? Show your work. A=F/m
29. A small engine causes a 0.9-kg model airplane to accelerate at a rate of 19m/s2. What is the net force on the
model airplane? Show your work. F=ma
30.
A 31-kilogram canoe broke free of its dock and is now floating downriver at a speed of 0.2 m/s. What is the
canoe’s momentum? Show your work. p=mv
31.
Why does a biker have to pedal harder to travel at a constant speed into the wind on a windy
day compared to traveling on the same road at the same speed on a calm day?
ESSAY
31. ANS:
On both the calm and windy days, the net force on the biker is zero because the biker is traveling at constant
speed. On a calm day, the biker must pedal so that the forward-directed force applied to the bike balances the
forces of friction opposing the forward motion. The friction forces primarily take the form rolling friction and
fluid friction. On a windy day, the fluid friction force is much greater, so the rider must pedal harder to
maintain the same constant speed.