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inn [45]
3 years ago
15

A student wearing frictionless in-line skates on a horizontal surface is pushed by a friend with a constant force of 47 N. How f

ar must the student be pushed, starting from rest, so that her final kinetic energy is 354 J ?
Physics
1 answer:
Novosadov [1.4K]3 years ago
4 0

Answer:

7.53 m

Explanation:

Force, F = 47 N

initial velocity, u = 0

Final kinetic energy, Kf = 354 J

Let the distance traveled by the student is s.

According to the work energy theorem,

Work done by all forces = Change in kinetic energy

Force x distance = final kinetic energy - initial kinetic energy

F x s = kf - ki

47 x s = 354

s = 7.53 m

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we know that

Power efficiency is defined as the ratio of the output power divided by the input power:

so

efficiency =\frac{ Power\  out}{Power\  in} *100

in this problem

Power\  out=45J\\ Power\  in=120J

Substitute in the formula above

efficiency =\frac{ 45}{120} *100

efficiency =37.5%

therefore

the answer is

the efficient is 37.5%

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Which statement describes the speed of electromagnetic waves?
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Their speed in a vacuum is a constant value.

Explanation:

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With 51 gallons of fuel in its tank, the airplane has a weight of 2390.7 pounds. What is the weight of the plane with 81 gallons
Shtirlitz [24]

Answer: 2561.7 pounds

Explanation:

If we assume the total weight of an airplane (in pounds units) as a <u>linear function</u> of the amount of fuel in its tank (in gallons) and we make a Weight vs amount of fuel graph, which resulting slope is 5.7, we can use the slope equation of the line:

m=\frac{Y-Y_{1}}{X-X_{1}}  (1)

Where:

m=5.7 is the slope of the line

Y_{1}=2390.7pounds is the airplane weight with  51 gallons of fuel in its tank (assuming we chose the Y axis for the airplane weight in the graph)

X_{1}=51gallons is the fuel in airplane's tank for a total weigth of 2390.7 pounds (assuming we chose the X axis for the a,ount of fuel in the tank in the graph)

This means we already have one point of the graph, which coordinate is:

(X_{1},Y_{1})=(51,2390.7)

Rewritting (1):

Y=m(X-X_{1})+Y_{1}  (2)

As Y is a function of X:

Y=f_{(X)}=m(X-X_{1})+Y_{1}  (3)

Substituting the known values:

f_{(X)}=5.7(X-51)+2390.7  (4)

f_{(X)}=5.7X-290.7+2390.7  (5)

f_{(X)}=5.7X+2100  (6)

Now, evaluating this function when X=81 (talking about the 81 gallons of fuel in the tank):

f_{(81)}=5.7(81)+2100  (7)

f_{(81)}=2561.7  (8)   This means the weight of the plane when it has 81 gallons of fuel in its tank is 2561.7 pounds.

3 0
3 years ago
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