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Lana71 [14]
3 years ago
15

How much work must be done to stop a 1075-kg car traveling at 115 km/h ? Express your answer to two significant figures and incl

ude the appropriate units
Physics
1 answer:
jok3333 [9.3K]3 years ago
6 0

Answer:

Work done on the car will be 548440.9463 J

Explanation:

We have given mass of the car m = 1075 kg

As the car finally stops so final velocity of the car v_f=0m/sec

Initial velocity of car u = 115 km/hr =115\times \frac{5}{18}=31.943m/sec

Work done is equal to change in kinetic energy

So work done =\frac{1}{2}mv_f^2-\frac{1}{2}mv_i^2

==\frac{1}{2}m(v_f^2-v_i^2)=\frac{1}{2}\times 1075\times (0^2-31.943^2)=-548440.946J

As the work done is negative so work is done on the car to stop it .

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You observe that a negatively charged plastic pen repels a charged piece of magic tape. You then observe that the same piece of
hichkok12 [17]

Answer:

(2) The excess negative charge from the sphere spread out all over your body.

(7) After you touched it, the metal sphere was very nearly neutral.

Explanation:

Plastic pen repels magic tape so magic tape is also  negatively charged . Further , magic tape repels small metal sphere that means small sphere also is negatively charged.

Now when small sphere is touched by a man insulated from ground , the charge is distributed between man and small sphere according to their capacitance .

Since human body will have greater capacitance ,it will acquire larger share of charge . Sphere being of very small size will retain very less charge and it will become almost neutral . Hence it will be   attracted by  charged tape .

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3 years ago
A 90 kg painter is standing on a horizontal wooden scaffolding of length 10 m, which is supported on each end by a rope. The pai
RSB [31]

Explanation:

For equilibrium, \sum M = 0.

So,   8 m \times mg - (10 m) T_{1} = 0

             T_{1} = \frac{8 \times mg}{10}

                        = \frac{8 \times 90 \times 9.8}{10}

                        = 705.6 N

Also, for equilibrium \sum F_{y} = 0

              T_{1} + T_{2} - mg = 0

or,         T_{2} = mg - T_{1}

                        = 90 \times 9.8 - 705.6

                        = 176.4 N

Thus, we can conclude that the tension in the first rope is 176.4 N.

8 0
3 years ago
Under the influence of its drive force, a snowmobile is moving at a constant velocity along a horizontal patch of snow. When the
balandron [24]

Answer:

a) Δx = 11.6 m

b) t = 3.9 s

Explanation:

a)

  • Since the snowmobile is moving at constant speed, and the drive force is 195 N, this means that thereis another force equal and opposite acting on it, according to Newton's 2nd Law, due to there is no acceleration present in the horizontal direction .
  • This force is just the force of kinetic friction, and is equal to -195 N (assuming the positive direction as the direction of the movement).
  • Once the drive force is shut off, the only force acting on the snowmobile remains the friction force.
  • According Newton's 2nd Law, this force is causing a negative acceleration (actually slowing down the snowmobile) that can be found as follows:

       a = \frac{F_{fr} }{m} = \frac{-195N}{128kg} = -1.5 m/s2 (1)

  • Assuming the friction force keeps constant, we can use the following kinematic equation in order to find the distance traveled under this acceleration before coming to an stop, as follows:

       v_{f} ^{2}  -v_{o} ^{2} = 2* a* \Delta x (2)

  • Taking into account that vf=0, replacing by the given (v₀) and a from (1), we can solve for Δx, as follows:

       \Delta x =- \frac{v_{o}^{2}}{2*a} =- \frac{(5.90m/s)^{2}}{2*(-1.5m/s2)} = 11.6 m (3)

b)

  • We can find the time needed to come to an stop, applying the definition of acceleration, as follows:

       v_{f} = v_{o} + a*\Delta t (4)

  • Since we have already said that the snowmobile comes to an stop, this means that vf = 0.
  • Replacing a and v₀ as we did in (3), we can solve for Δt as follows:

       \Delta t = \frac{-v_{o} }{a} = \frac{-5.9m/s}{-1.5m/s2} = 3.9 s   (5)

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Natalija [7]

Answer:

50% of it .

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50% of it is illuminated by the Sun.

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