A man drags a 71-kg crate across the floor at a constant velocity by pulling on a strap attached to the bottom of the crate. The
1 answer:
Answer:
T = 540 N (to two significant digits)
Explanation:
Let the crate dimension L be from strap attachment to floor contact
Let T be the strap tension
sum moments about the floor contact point to zero
mg[½Lcos25] - Tsin61[Lcos25] + Tcos61[Lsin25] = 0
L is common to all terms, so divides out.
½(71)(9.8)cos25 = T(sin61cos25 - cos61sin25)
T = (71)(9.8)cos25 / (2(sin61cos25 - cos61sin25))
T = 536.428020...
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Answers:
1)
2)
Explanation:
1) Acceleration is defined as the variation of Velocity
in time
:
(1)
A body also has acceleration when it changes its direction.
In this case we have a bus with a velocity of 60m/s to the east, that accelerates in a time 10s. So, we have to find the bus's acceleration:
(2)
(3) This is the bus's accelerration
2) Now we have a car that accelerates to the west in order to reach a speed of
in the same direction, and we have to find the time
it takes to the car to reach that velocity.
Therefore we have to find from (1):
(4)
(5)
Finally:
(6)
<span> (a) does an electric field exert a force on a stationary charged object?
Yes. The force exerted by an electric field of intensity E on an object with charge q is
</span>
<span>As we can see, it doesn't depend on the speed of the object, so this force acts also when the object is stationary.
</span><span>(b) does a magnetic field do so?
No. In fact, the magnetic force exerted by a magnetic field of intensity B on an object with charge q and speed v is
</span>
where
is the angle between the direction of v and B.
As we can see, the value of the force F depends on the value of the speed v: if the object is stationary, then v=0, and so the force is zero as well.
<span>(c) does an electric field exert a force on a moving charged object?
Yes, The intensity of the electric force is still
</span>
<span>as stated in point (a), and since it does not depend on the speed of the charge, the electric force is still present.
</span><span>(d) does a magnetic field do so?
</span>Yes. As we said in point b, the magnetic force is
And now the object is moving with a certain speed v, so the magnetic force F this time is different from zero.
<span>(e) does an electric field exert a force on a straight current-carrying wire?
Yes. A current in a wire consists of many charges traveling through the wire, and since the electric field always exerts a force on a charge, then the electric field exerts a force on the charges traveling through the wire.
</span><span>(f) does a magnetic field do so?
Yes. The current in the wire consists of charges that are moving with a certain speed v, and we said that a magnetic field always exerts a force on a moving charge, so the magnetic field is exerting a magnetic force on the charges that are traveling through the wire.
</span><span>(g) does an electric field exert a force on a beam of moving electrons?
Yes. Electrons have an electric charge, and we said that the force exerted by an electric field is
</span>
<span>So, an electric field always exerts a force on an electric charge, therefore on an electron beam as well.
</span><span>(h) does a magnetic field do so?
Yes, because the electrons in the beam are moving with a certain speed v, so the magnetic force
</span>
<span>is different from zero because v is different from zero.</span>
Yes. The force exerted by an electric field of intensity E on an object with charge q is
</span>
<span>As we can see, it doesn't depend on the speed of the object, so this force acts also when the object is stationary.
</span><span>(b) does a magnetic field do so?
No. In fact, the magnetic force exerted by a magnetic field of intensity B on an object with charge q and speed v is
</span>
where
As we can see, the value of the force F depends on the value of the speed v: if the object is stationary, then v=0, and so the force is zero as well.
<span>(c) does an electric field exert a force on a moving charged object?
Yes, The intensity of the electric force is still
</span>
<span>as stated in point (a), and since it does not depend on the speed of the charge, the electric force is still present.
</span><span>(d) does a magnetic field do so?
</span>Yes. As we said in point b, the magnetic force is
And now the object is moving with a certain speed v, so the magnetic force F this time is different from zero.
<span>(e) does an electric field exert a force on a straight current-carrying wire?
Yes. A current in a wire consists of many charges traveling through the wire, and since the electric field always exerts a force on a charge, then the electric field exerts a force on the charges traveling through the wire.
</span><span>(f) does a magnetic field do so?
Yes. The current in the wire consists of charges that are moving with a certain speed v, and we said that a magnetic field always exerts a force on a moving charge, so the magnetic field is exerting a magnetic force on the charges that are traveling through the wire.
</span><span>(g) does an electric field exert a force on a beam of moving electrons?
Yes. Electrons have an electric charge, and we said that the force exerted by an electric field is
</span>
<span>So, an electric field always exerts a force on an electric charge, therefore on an electron beam as well.
</span><span>(h) does a magnetic field do so?
Yes, because the electrons in the beam are moving with a certain speed v, so the magnetic force
</span>
<span>is different from zero because v is different from zero.</span>