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In a rocket, the kinetic energy imparted to the consumed and ejected fuel is wasted as far as propelling the rocket is concerned. The useful power is equal to the product of the force available to propel the rocket and the speed of the rocket. If v is the speed of the rocket and u is the relative speed of the expelled fuel, show that the
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Vector Mechanics for Engineers: Dynamics
- 8. Lost in the Equations 2. A rectangular container is initially one-third full of water, and an empty cylindrical bucket of mass m = 150 g is initially floating in it. Now, Franco turns the faucet on, which deposits water into the bucket with a constant mass rate o = 63.1 g/s. As expected, the water level of the container rises. After some time, the top of the bucket eventually reaches the water level of the container and the water level of the container decreases sharply. The bucket then sinks to the floor of the container and is completely submerged. You are given that the water has density p = 1025 kg/m³. The cross-sectional areas of the rectangular container and the circular bucket are A = 100 cm² and a = 49.0 cm² respectively. If the faucet doesn't stop flowing, find the rate by which the rectangular container's water level increases before the sharp decrease in water level.arrow_forwardThe pumping power of the human heart is approximately 2W (assuming a normal cardiac output of 5 liters/min). Like any pump, however, the heart is not 100% efficient, and, therefore, the power that is supplied to the heart muscle will actually exceed 2W. In this question we will estimate the heart’s pumping efficiency η by calculating how much energy is supplied to the heart muscle from the blood.(Note that the heart muscle has its own vasculature, called the coronarycirculation.) (a) When we calculated the pumping power of the heart, we only considered the head gain across the heart from the pressure increase. In general, there could also be changes in elevation (very small) and in kineticenergy. Estimate the ratio of kinetic energy head to pressure head at peaksystole, when pressure is 120 mmHg and blood velocity is 100 cm/s.Can we safely neglect kinetic energy gains in calculating pumpingpower?(b) At rest, the coronary blood flow is 225 ml/min, and 65% of the O2 isremoved from the…arrow_forwardI4arrow_forward
- A water turbine is used to generate electricity across a dam. The mass flowrate of water at the river is 10000 kg/s and the efficiency of the turbine and generator are 80% and 90% respectively. Knowing that the turbine generate a total of 10 MW, determine the height h , considering the that the system has a total loss of 10% of the total energy generated by the power plant. Consider: Density of water = 1000 kg/m³ and g= 9.81m²/sarrow_forwardWater accelerated by a nozzle to 33 m/s strikes the vertical back surface of a cart moving horizontally at a constant velocity of 9 m/s in the flow direction. The mass flow rate of water through the stationary nozzle is 30 kg/s. After the strike, the water stream splatters off in all directions in the plane of the back surface. Determine the force that needs to be applied by the brakes of the cart to prevent it from accelerating. If this force were used to generate power instead of wasting it on the brakes, determine the maximum amount of power that could ideally be generated.arrow_forwardPROBLEM 8. The total weight of space shuttle including its payload mass and the empty external tank, and its empty two solid rocket boosters is mo = 428,100 lb. It is known that the external tank and the two solid rocket boosters initially holds m,(0) = 3,728,875 lb of fuel (that is the total weight of solid fuel plus liquid oxygen and hydrogen). The shuttle consumes its liquid and solid fuels at a constant rate of A = 14,300 lb/s. Also, it is known that the shuttle thrust force is F, = 400,000 lb. (a) Use the Newton's 2nd law below to find the second order differential equation that describes the vertical position y of the space shuttle as a function of time. The shuttle is launched vertically upward from the ground as shown below, with the positive direction upward and the air resistance is ignored. The Earth's gravitational acceleration on its surface is g = 32.2 ft/s² and its radius is R = 4000 miles. Frotat (t) = [m(t). v] Fthrust Where, - Frotat(t) is the net force acting on the…arrow_forward
- Estimate the maximum horizontal distance you can throw a baseball (m = 0.145 kg) if you throw it at an angle of a0 = 45° above the horizontal in order to achieve the maximum range. (a) What is the kinetic energy of the baseball just after it leaves your hand? Ignore air resistance and the small distance the ball is above the ground when it leaves your hand. Take the zero of potential energy to be at the ground. (b) At the ball’s maximum height, what fraction of its total mechanical energy is kinetic energy and what fraction is gravitational potential energy? (c) If you throw the baseball at an initial angle of 60° above the horizontal, at its maximum height what fraction of its total energy is kinetic energy and what fraction is gravitational potential energy? (d) What fraction of the total mechanical energy is kinetic energy at the maximum height in the limiting cases of a0 = 0° and a0 = 90°?arrow_forwardConsider an airplane with a jet engine attached to the tail section that expels combustion gases at a rate of 18 kg/s with a velocity of V = 300 m/s relative to the plane. During landing, a thrust reverser (which serves as a brake for the aircraft and facilitates landing on a short runway) is lowered in the path of the exhaust jet, which deflects the exhaust rearward 120 degrees, as shown below. Determine (a) the thrust (forward force) that the engine produces prior to the insertion of the thrust reverser and (b) the braking force produced after the thrust reverser is deployed.arrow_forward5. A 60-kg ice skater is standing on ice with ice skates (negligible friction). She is holding a flexible hose (essentially weightless) that directs a 2-cm-diameter stream of water horizontally parallel to her skates. The water velocity at the hose outlet is 10 m/s relative to the skater. If she is initially standing still, determine: (a) the velocity of the skater and the distance she travels in 5 s., (b) how long it will take to move 5 m and the velocity at that moment. Ice skater 10 m/s D = 2 cmarrow_forward
- 1. A reversing elbow used to deflect water flow at a rate of 14 kg/s in a horizontal pipe to make a U-turn before it is discharged into the atmosphere, as shown in Figure 1. The cross-section area of the elbow is 113 cm² at the inlet and 7 cm² at the outlet. The elevation difference between the centers of the outlet and inlet is 30 cm. Neglecting the weight of the elbow and the water in it and assuming the flow is frictionless, determine the anchoring force needed to hold the elbow in place. mv₂ mV₁ O Figure 1.arrow_forwardHow much work is done on helicopter by gravity? How much work is done on it by the upward thrust force? What is the magnitude of the upward thrust force (assumed constant)?arrow_forwardA body has an initial linear momentum of (30i – 50j) kgm/s. A force of (6i – 10j) N is applied to the body for 10 s. What will the linear momentum be after the application of this load? OG-(90i – 150j) kgm/s OG-(-90i + 150j) kgm/s OG-(36i – 60j) kgm/s OG-(-36i + 60j) kgm/sarrow_forward
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