robert7248
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At the beginning of a bobsled race, teammates push their bobsled along the track before jumping into it.

a. Before the teammates jump in, they push the bobsled (m = 150 kg) from rest to a speed of 4.2 m/s. How much kinetic energy does the bobsled gain?

b. How much work did the bobsled team do? Explain how you found the answer.

c. If the teammates pushed the bobsled with a force of 500 N, over what distance did they apply the force?

d. Later, the bobsled is racing down the track at a speed of 28 m/s. With the team in it, the bobsled has a total mass of 430 kg. How much work must be done by air resistance to slow down the bobsled to 25 m/s?

Respuesta :

a) KE=1/2 mv^2=1/2*150*4.2^2=1323 J

b) Work-energy theorem states that work equals the gained KE, so W=KE=1323 J

c) d=W/F=1323/500=2.65 m

d) Again apply work-energy theorem:

W=1/2*m(v2^2-v1^2)=1/2*430*(25^2-28^2)=--34.185 J

a. The kinetic energy gain of the bobsled is 1323 J.

b. The work done by the bobsled team is 1323 J.

c. The distance over which the force applied is 2.65 m.

d. The work must be done by air resistance to slow down the bobsled to 25 m/s will be  -34.185 J.

What is Work energy theorem?

It states that the work done in moving a body is equal to the change in kinetic energy of the body.

Kinetic energy = 1/2 mv²

a. Before the teammates jump in, they push the bobsled (m = 150 kg) from rest to a speed of 4.2 m/s.

Kinetic energy, K.E =1/2 x 150 x 4.2²

                        K.E=1323 J

Thus, the kinetic energy gain of the bobsled is 1323 J.

b. From Work-energy theorem, work done = gained KE,

W= K.E=1323 J

Thus, work done by the bobsled team is 1323 J.

c. If the teammates pushed the bobsled with a force of 500 N,

distance =Work done / Force

d=1323/500

d=2.65 m

Thus, the distance over which the force applied is 2.65 m.

d) Applying work-energy theorem, we have

W=1/2 x m(v₂²-v₁²)

W =1/2 x 430 x (25²-28²)

W = -34.185 J

Thus, work must be done by air resistance  is  -34.185 J.

Learn more about work energy theorem.

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