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Physics 5.4-5.7

Uria Lee avatar Uria Lee
25 July 2022
4.7 (114 reviews)
23 test answers

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question
Force
answer
A push or pull exerted on an object
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Pressure
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The amount of force exerted per unit area of a surface
question
Which produces more pressure on the ground, a person standing up or the same person lying down?
answer
The person standing up.
question
The force of gravity is twice as great on a 2kg rock as a 1kg rock. Why does the 2kg rock not fall with twice the acceleration?
answer
The ratio of weight to mass is the same.
question
Why do a coin and feather fall with different accelerations in the presence of air?
answer
The air resistance diminishes the net force on the objects. The air resistance equals the weight of the feather faster than the weight of the coin, therefore the feather slows down and reaches terminal speed (or velocity) faster and falls slower.
question
Describe friction.
answer
It is a for e and affects motion. When two solid objects come into opposing motions, and there are irregularities on the surface, it requires force to overcome the friction. It can impact solids, fluids, air.
question
Air resistance
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The friction acting on something moving through air.
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What is the rate of velocity and acceleration when the friction force applied to the front of a plane equals the amount of applied force coming from the jet engines?
answer
The velocity is constant and the acceleration equals zero.
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Why do a coin and a feather in a vacuum tube fall with the same acceleration?
answer
Without any air resistance, both objects freely fall with the same acceleration because the net force on each object is only its weight and the ratio of weight to mass is the same for both.
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How much air resistance acts on a 100-N bag of nails that falls at its terminal speed?
answer
100-N
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How do the air resistance and the weight of a falling object compare when terminal speed is reached?
answer
They are the same. The force of air resistance equals the weight of the object (or the force of gravity).
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All other things being equal, why does a heavy sky diver have a terminal speed greater than a light sky diver? What can be done so that the terminal speeds are equal?
answer
The lighter sky diver reaches terminal speed faster because less air resistance is required. The heavier sky diver requires more air resistance to equal their weight and reach terminal speed. If the lighter sky diver dives feet or head first, and the heavier sky diver spreads their arms and legs, they can reach equal terminal speeds.
question
What is the net force when the object encounters 15N of air resistance?
answer
10N
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When it falls fast enough to encounter 25N of air resistance?
answer
25N or terminal speed / velocity
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How do you calculate force?
answer
Force = mass x acceleration
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How do you calculate acceleration?
answer
Acceleration = force / mass
question
Calculate the acceleration if you push with 20N horizontal force on a 2kg block in a horizontal friction-free air table.
answer
10 m/s2
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What acceleration occurs if the friction force is 4N?
answer
8 m/s2???
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Calculate the horizontal force that must be applied to a 1kg puck to make it accelerate on a horizontal friction-free air table with the same acceleration it would have if it were dropped freely and fell.
answer
1 N??
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Calculate the horizontal force that must be applied to produce an acceleration of 1.8g for a 1.2g puck on a horizontal friction-free air table.
answer
2.16 N
question
A horizontal force of 100 N is required to push a crate across a factory floor at a constant speed. What is the net force acting on the crate? What is the force of friction acting on the crate?
answer
Net force is 0, friction force is 100 N.
question
What will be the acceleration of a sky diver when air resistance is half the weight of the sky diver?
answer
.5 m/s2?
question
An occupant of a car has a chance of surviving a crash if the deceleration during the crash is not more than 30g. Calculate the force on a 70kg person decelerating at this rate.
answer
2100 N