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Alex
3 years ago
15

Eric has a mass of 70 . He is standing on a scale in an elevator that is accelerating downward at 1.7 . What is the approximate

reading on the scale?
A. 0
B. 570N
C. 690N
D. 810N
Physics
1 answer:
pychu [463]3 years ago
5 0

Answer:

B)

Explanation:

The value the scale shows is the reaction force to the normal force (they are equal by Newton's 3rd Law) that the scale exerts on Eric.

The forces on Eric are his weight (downward) and this normal force (upward), so we can write the net force over him as (also using Newton's 2nd Law):

F=W-N=ma

which means

N=W-ma=mg-ma=m(g-a)

and for our values this is:

N=mg-ma=(70kg)(9.8m/s^2-1.7m/s^2)=567N

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3 years ago
A student team is to design a human powered submarine for a design competition. The overall length of the prototype submarine is
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Answer:

a) The speed is 61.42 m/s

b) The drag force is 10.32 N

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a) The Reynold´s number for the model and prototype is:

Re_{m} =\frac{p_{m}V_{m}L_{m}   }{u_{m} }

Re_{p} =\frac{p_{p}V_{p}L_{p}   }{u_{p} }

Equaling both Reynold's number:

\frac{p_{p}V_{p}L_{p}   }{u_{p} }=\frac{p_{m}V_{m}L_{m}   }{u_{m} }

Clearing Vm:

V_{m} =\frac{p_{p}V_{p}L_{p} u_{m}   }{u_{p} p_{m} L_{m} }=\frac{999.1*0.56*8*1.849x10^{-5} }{1.138x10^{-3}*1.184*1 } =61.42m/s

b) The drag force is:

\frac{F_{Dm} }{p_{m}V_{m}^{2}L_{m}^{2}     } =\frac{F_{Dp} }{p_{p}V_{p}^{2}L_{p}^{2}     } \\F_{Dp} =\frac{F_{Dp}p_{p}V_{p}^{2}L_{p}^{2} }{p_{m}V_{m}^{2}L_{m}^{2}     } \\F_{Dp}=\frac{2.3*999.1*0.56^{2} *8^{2} }{1.184*61.42^{2}*1^{2}  } =10.32N

8 0
3 years ago
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3 years ago
When the saw slices wood, the wood exerts a 104-N force on the blade, 0.128 m from the blade’s axis of rotation. If that force i
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Answer:

Explanation:

When saw slices wood by exerting a force on the wood , wood also exerts a reaction force on the saw in opposite direction which is equal to the force of action that is 104 N.

So torque exerted by wood on the blade

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With an initial velocity of 20km per hour a car accelerated at 8m/s2 for 10s,what is the position of the car at the end of 10s
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\\ \sf\longmapsto s=ut+\dfrac{1}{2}at^2

\\ \sf\longmapsto s=5.5(10)+\dfrac{1}{2}(8)(5.5)^2

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