Problem 129
To make a batch of cookies, you mix half a bag of chocolate chips into a bowl of cookie dough, exerting a \(21-\mathrm{N}\) force on the stirring spoon. Assume that your force is always in the direction of motion of the spoon. (a) What power is needed to move the spoon at a speed of \(0.23 \mathrm{~m} / \mathrm{s}\) ? (b) How much work do you do if you stir the mixture for \(1.5 \mathrm{~min}\) ?
Problem 130
A particle moves without friction. At point A the particle has a kinetic energy of \(12 \mathrm{~J}\); at point B the particle is momentarily at rest, and the potential energy of the system is \(25 \mathrm{~J}\); at point \(\mathrm{C}\) the potential energy of the system is \(5 \mathrm{~J}\). (a) What is the potential energy of the system when the particle is at point \(A\) ? (b) What is the kinetic energy of the particle at point \(C\) ?
Problem 131
When a ball of mass \(m\) is dropped from rest from a height \(h\), its kinetic energy just before landing is KE. Now, suppose a second ball of mass \(4 m\) is dropped from rest from a height \(h / 4\). (a) Just before ball 2 lands, is its kinetic energy \(4 K E, 2 K E, K E, K E / 2\), or \(K E / 4\) ? (b) Choose the best explanation from among the following: A. The two balls have the same initial energy. B. The more massive ball will have the greater kinetic energy. C. The lower drop height results in a reduced kinetic energy.
Problem 131
Predict \& Explain When a ball of mass \(m\) is dropped from rest from a height \(h\), its kinetic energy just before landing is \(K E\). Now, suppose a second ball of mass \(4 m\) is dropped from rest from a height \(h / 4\). (a) Just before ball 2 lands, is its kinetic energy \(4 K E, 2 K E, K E, K E / 2\), or \(K E / 4\) ? (b) Choose the best explanation from among the following: A. The two balls have the same initial energy. B. The more massive ball will have the greater kinetic energy. C. The lower drop height results in a reduced kinetic energy.
Problem 132
Meteorite On October 9,1992, a \(12=\mathrm{kg}\) meteorite struck a car in Peekskill, New York, creating a dent about \(22 \mathrm{~cm}\) deep, as shown in Figure 6.16. If the initial speed of the meteorite was \(550 \mathrm{~m} / \mathrm{s}\), what was the average force exerted on the meteorite by the car?
Problem 133
(a) At what rate must you lift a \(3.6-\mathrm{kg}\) container of milk (1 gallon) if the power output of your arm is to be \(22 \mathrm{~W}\) ? (b) How long does it take to lift the milk container through a distance of \(1.0 \mathrm{~m}\) at this rate?
Problem 133
(a) At what rate must you lift a 3.6-kg container of milk (1 gallon) if the power output of your arm is to be 22 W? (b) How long does it take to lift the milk container through a distance of 1.0 m at this rate?
Problem 134
A catapult launcher on aircraft carrier accelerates a jet from rest to \(72 \mathrm{~m} / \mathrm{s}\). The work done by the catapult during the launch is \(7.6 \times 10^{7} \mathrm{~J}\). (a) What is the mass of the jet? (b) If the jet is in contact with the catapult for \(2.0 \mathrm{~s}\), what is the power output of the catapult?
Problem 134
Catapult Launcher A catapult launcher on an aircraft carrier accelerates a jet from rest to 72 m>s. The work done by the catapult during the launch is 7.6 * 107 J. (a) What is the mass of the jet? (b) If the jet is in contact with the catapult for 2.0 s, what is the power output of the catapult?
Problem 137
Think \& Calculate A pitcher accelerates a 0.14-kg hardball from rest to \(25.5 \mathrm{~m} / \mathrm{s}\) in \(0.075 \mathrm{~s}\). (a) How much work does the pitcher do on the ball? (b) What is the pitcher's power output during the pitch? (c) Suppose the ball reaches \(25.5 \mathrm{~m} / \mathrm{s}\) in less than \(0.075 \mathrm{~s}\). Is the power produced by the pitcher in this case more than, less than, or the same as the power found in part (b)? Explain.
