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podryga [215]
2 years ago
9

A steel playground slide is 5.25 m long and is raised 2.75 m on one end. A 45.0 kg child slides down from the top starting at re

st. The final speed of the child at the bottom is 6.81 m/s. Find the average force of friction between the child and the slide.
Physics
1 answer:
Temka [501]2 years ago
8 0

Answer:

F=32.24N

Explanation:

From the question we are told that:

Height h= 2.75 m

Lengthl = 5.25 m

Mass m=45kg

Final speed v_f=6.81

Generally the equation for Potential Energy P.E is mathematically given by

P.E=mgh

Therefore

Initial potential energy

P.E_1=45*9.8*2.75 \\\\P.E_1= 1212.75 J

Generally the equation for Kinetic Energy K.E is mathematically given by

K.E=0.5mv^2

Therefore

Final kinetic energy

K.E_2= 1/2*45*6.81*6.81 \\\\K.E_2= 1043.46J

Generally the equation for Work_done is mathematically given by

W=P.E_1-K.E_2\\\\W=169.3

Therefore

F=\frac{W}{d}\\\\F=\frac{169.3}{5.25}

F=32.24N

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Answer:

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(b) 37.5 KJ

Explanation:

(a)

From the law of conservation of momentum, Initial momentum=Final momentum

mV_1+3mV_2=(m+3m)V_f=4mV_f

V_1+3V_2=4V_f and making V_f the subject then

V_f=\frac {V_1+3V_2}{4} and since V_1 is initial velocity of car, value given as 4 m/s, V_2 is the initial velocity of the three cars stuck together, value given as 2 m/s and v_f is the final velocity which is unknown. By substitution

V_f=\frac {4+(3\times2)}{4}=2.5 m/s

(b)

Initial kinetic energy is given by

\frac {mV_1^{2}}{2}+\frac {3mV_2^{2}}{2}=\frac {m(V_1^{2}+3V_2^{2}}{2}=\frac {2.5\times 10^{4}(4^{2}+3(2^{2}))}{2}=350\times10^{3} J= 350 KJ

Final kinetic energy is given by

\frac {4mV_f^{2}}{2}=\frac {4\times 2.5\times 10^{4}\times 2.5^{2}}{2}=312.5\times 10^{3} J=312.5 KJ

The energy lost is given by subtracting the final kinetic energy from the initial kinetic energy hence

Energy lost=350-312.5=37.5 KJ

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