Download 1 Net Force, Acceleration and Mass Date ______ When two objects

Net Force, Acceleration and Mass Date ______
When two objects are in contact, the magnitude of the force exerted on object 1 by object 2 is ________________ to the magnitude of the force SIMULTANEOUSLY exerted on object 2 by object 1. These forces are _______________ in direction.
The acceleration of the object depends on the ________ _____________ on the object and the _______________ of the object.
The acceleration of an object is ______________ proportional to the net force acting on the object.
The acceleration of an object is ______________ proportional to the object's mass.
If equal forces are applied to two objects of different masses, the object with less mass will experience a _______________ acceleration and the object with more mass will experience a _________________ acceleration.
In Chapter 2 acceleration was the
rate of change of velocity:
a = vf ­ vi
Δt
In Chapter 4 acceleration is the ratio of the net force to mass: a = Fnet
m
The CAUSE of the acceleration is the force which produces the rate of change in velocity.
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Net force = ____
Net force = ____
NO ________
in motion.
Object _________________
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This relationship can be written in equation form.
a = Fnet
or
Fnet = ma where Fnet is a vector sum of all the forces on an
m object. It call the net force.
Net Force(N) Mass (kg)
Acceleration
(m/s2 )
1.
10
2
2.
20
2
3.
20
4
4.
5.
2
10
5
10
When the mass is constant and the net force is doubled, the acceleration __________
When the net force is constant and the mass doubles, the acceleration ____________
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Two identical spring loaded dart guns are
simultaneously fired straight downward.
One fires a regular dart; the other a weighted
dart. Which dart hits the ground first?
Why?
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Net Force, Acceleration, and Mass Practice Problems:
Two people with the same mass of 50 kg are riding in a pickup truck at 20 m/s to the right.
They are brought to an abrupt stop in a head on collision with a drunk driver who has crossed the divider line.
One person wears a seat belt and is brought to a stop in 0.1 second.
The other person is not wearing a seat belt and is brought to a stop by the dashboard in 0.01 seconds.
Draw a picture of the collision and the force pair between the truck and the drunk driver.
1) What is the acceleration of the person who comes to a stop wearing the seat belt?
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2) What is the net force exerted by the seat belt to bring the first person to a stop?
3) What is the acceleration of the person who comes to a stop by hitting the dashboard?
4) What is the net force exerted by the dashboard to bring the second person to a stop?
5) What is the weight of the person stopped by the dashboard? 6) Compare his weight to the force of the dashboard.
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Calculating Acceleration from Free Body Diagrams
A desk is pulled along a smooth floor.
FN = _______
Fa = 50 N
Ff = 10 N
Fg = ________
m = 8 kg
Fnet = _____________
a = _____________
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An ball slows down as it rolls across the floor.
FN = _______
Ff = 8 N
Fg = 5 N
m = ________
Fnet = _____________
a = _____________
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This object is on a level surface. What is its motion?
FN = _______
Ff = 15 N
m = 6 kg
Fa = 15 N
Fg = ________
a = 0 m/s2
Fnet = _____________
This object is ___________________________.
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Fnet = 0 N; Fgrav = 98 N; Fnorm = 98 N; Ffrict = 19.6 N; Fapp = 19.6 N
When the velocity is constant, a = 0 m/s/s and Fnet = 0 N
Since the mass is known, Fgrav can be found (Fgrav = m • g = 10 kg • 9.8 m/s/s). Since there is no vertical acceleration, normal force = gravity force. Once Fnorm is known, Ffrict can be found using Ffrict = "mu" •Fnorm. Since there is no horizontal acceleration, Ffrict = Fapp = 19.6 N
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