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Physics MCQs thread.

arlery

arlery

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A force of 1000 N is needed to lift the hook of a crane at a steady velocity. The crane is then used
to lift a load of mass 1000 kg at a velocity of 0.50 m s–1.
How much of the power developed by the motor of the crane is used in lifting the hook and the
load? Assume that the acceleration of free fall g is equal to 10 m s–2.

A 5.0 kW
B 5.5 kW
C 20 kW
D 22 kW


Why is the answer B??
 
U

unique840

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arlery said:
A force of 1000 N is needed to lift the hook of a crane at a steady velocity. The crane is then used
to lift a load of mass 1000 kg at a velocity of 0.50 m s–1.
How much of the power developed by the motor of the crane is used in lifting the hook and the
load? Assume that the acceleration of free fall g is equal to 10 m s–2.

A 5.0 kW
B 5.5 kW
C 20 kW
D 22 kW


Why is the answer B??
Click to expand...

power= Fv
total force is 1000 + (1000*10)
so power is 11000*0.5
5.5kw
 
arlery

arlery

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Can any one please help me with this??
 

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H

Hateexams93

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Two springs P and Q both obey Hooke’s law. They have spring constants 2k and k respectively.
The springs are stretched, separately, by a force that is gradually increased from zero up to a
certain maximum value, the same for each spring. The work done in stretching spring P is WP,
and the work done in stretching spring Q is WQ.
How is WP related to WQ?
A WP =  0.25WQ B WP = 0.5 WQ C WP = 2WQ D WP = 4WQ
 
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xHazeMx

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arlery said:
Can any one please help me with this??
Click to expand...
lol nice question, consider ur eyes as the positive plate and the question as the negative plate. u should get it as D
 
arlery

arlery

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A source of e.m.f. of 9.0 mV has an internal resistance of 6.0 Ω.
It is connected across a galvanometer of resistance 30 Ω.
What will be the current in the galvanometer?
A 250 μA
B 300 μA
C 1.5 mA
D 2.5 mA

Why is the answer A?
 
Y

yubakkk

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Hateexams93 said:
Two springs P and Q both obey Hooke’s law. They have spring constants 2k and k respectively.
The springs are stretched, separately, by a force that is gradually increased from zero up to a
certain maximum value, the same for each spring. The work done in stretching spring P is WP,
and the work done in stretching spring Q is WQ.
How is WP related to WQ?
A WP =  0.25WQ B WP = 0.5 WQ C WP = 2WQ D WP = 4WQ
Click to expand...
hey first find f for both using f=kx x iz same for both
then use wd =1/2fx
 
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yubakkk

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A source of e.m.f. of 9.0 mV has an internal resistance of 6.0 Ω.
It is connected across a galvanometer of resistance 30 Ω.
What will be the current in the galvanometer?
A 250 μA
B 300 μA
C 1.5 mA
D 2.5 mA
any one????
 
X

xHazeMx

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yubakkk said:
A source of e.m.f. of 9.0 mV has an internal resistance of 6.0 Ω.
It is connected across a galvanometer of resistance 30 Ω.
What will be the current in the galvanometer?
A 250 μA
B 300 μA
C 1.5 mA
D 2.5 mA
any one????
Click to expand...
TOTAL resistance = 30 + 6 = 36 ohms
e.m.f = 9 mV = 9 x 10^-3 V

V=IR

I = 9 x 10^-3 / 36 = 2.5 x 10^-4 = 250 μA
 
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