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Alex_Xolod [135]
3 years ago
7

A 1500 kg car begins sliding down a 5.0o inclined road with a speed of 30 km/h. The engine is turned off, and the only forces ac

ting on the car are a net frictional force from the road and the gravitational force. After the car has traveled 50 m along the road, its speed is 40 km/h.
(a) How much is the mechanical energy of the car reduced because of the net frictional force?
(b) What is the magnitude of that net frictional force?
Physics
1 answer:
Marina86 [1]3 years ago
4 0

Answer:

a) -23583J

b) 471.66N

Explanation:

Using the conservation energy theorem:

K_o+U_o+W_f=K_f+U_f\\W_f=K_f+U_f-(K_o+U_o)

The height is given by:

sin(\theta)=\frac{h}{d}\\\\h=50*sin(5^o)\\h=4.36m

substituting the values we have:

W_f=\frac{1}{2}*1500kg*((40-30)\frac{km}{h}*\frac{1000h.m}{3600km.s})^2+0-1500kg*9.8m/s^2*4.36m\\W_f=-23583J*

the work is defined by:

W_f=F_f*d*cos(\theta)

the force of the friction force is 180 degrees because it's opposite to the movement, so:

F_f=\frac{-23583J}{50m*cos(180)}\\F_f=471.66N

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A sphere is charged with electrons to -6 x 10^-6C. How many electrons make up this charge? The elemental charge is 1.6 x 10^-19
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Answer:

3.75*10^{-13}  electrons

Explanation:

The total charge Q is the sum of the charge of the N electrons contained in the sphere:

Q=N*q_{e}

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Two ice skaters stand together as illustrated in the attached figure. They "push off" and travel directly away from each other,
Tema [17]
By definition, the momentum is given by:
 p = m * v
 Where,
 m = mass
 v = speed.
 On the other hand,
 F = m * a
 Where,
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 a = acceleration:
 For the boy we have:
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 p1 = 36.19 Kg * (m / s)
 For the girl we have:
 p2 = m * v
 p2 = (F / a) * v
 p2 = ((480) / (9.81)) * (v)
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 Clearing v:
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 v = -0.74 m / s (negative because the velocity is in the opposite direction of the boy's)
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