#70 the aceerliot phase of its motion. Express your answer in (a) watts negative

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#70

the aceerliot phase of its motion. Express your answer in (a) watts negative and (b) horsepower. e68 In 2.0 minutes, a ski lift raises four skiers at constant speed to a height of 140 m. The average mass of each skier is 65 kg. What is the average power provided by the tension in the cable pulling the lift? a* 69. ssm The motor of a ski boat generates an average power of 7.50 × 104 W when the boat is moving at a constant speed of 12 m/s. When the boat is pulling a skier at the same speed, the engine must gen- erate an average power of 8.30 x 104 W. What is the tension in the tow rope that is pulling the skier? ** 70. A 1900-kg car experiences a combined force of air resistance and friction that has the same magnitude whether the car goes up or down a hill at 27 m/s. Going up a hill, the car's engine produces 47 hp more power to sustain the constant velocity than it does going down the same hill. At what angle is the hill inclined above the horizontal? Section 6.9 71. appli initial comp Work Done by a Variable Force ssm The drawing shows the force-displacement graph for two different bows. These graphs give the force that an archer must apply tho houctring (a) For which bow is more work required to ment

Explanation / Answer

Problem 70)

Given,

Mass of the car, m = 1900 kg

Velocity, v = 27 m/s

Let the angle be theta

Total resistance force = f

In upward direction,

Net force = mg sin(theta) + f

So, power, P = (mg sin(theta) + f ) v = (18620 sin(theta) + f ) 27

= 502740 sin(theta) + 27 f ......... (1)

In down direction,

Net force = ( f - mg sin(theta)

So, power P ' = ( f - mg sin(theta) v

= 27f - 502740 sin(theta) .......... (2)

According to problem , P = P ' + 47 hp

502740 sin(theta) + 27f = 27 f - 502740 sin(theta) + 47 hp

1005480 sin(theta) = 47 hp

= 47 x 746 W = 35062 W

sin(theta) = 0.03487

Theta = 1.998 degree ~ 2 degrees (Ans)

Comment in case any doubt please rate my answer .....

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