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Chapter 9: Q. 36 (page 229)
a. How much work does an elevator motor do to lift a kg elevator a height of m?
b. How much power must the motor supply to do this in s at constant speed?
a). work done by elevator motor is J
b). power isW
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A ice skater is gliding along the ice, heading due north at . The ice has a small coefficient of static friction, to prevent the skater from slipping sideways, but . Suddenly, a wind from the northeast exerts a force of on the skater.
a. Use work and energy to find the skater鈥檚 speed after gliding in this wind.
b. What is the minimum value of that allows her to continue moving straight north?
FIGURE is the kinetic-energy graph for a 2.0 kg object moving along the x-axis. Determine the work done on the object during each of the four intervals AB, BC, CD, and DE.
厂耻蝉补苍鈥檚 kg baby brother Paul sits on a mat. Susan pulls the mat across the floor using a rope that is angled above the floor. The tension is a constant N and the coefficient of friction is . Use work and energy to find Paul鈥檚 speed after being pulled m.
A 0.2 kg plastic cart and a 20 kg lead cart both roll without friction on a horizontal surface. Equal forces are used to push both carts forward a distance of 1 m, starting from rest. After traveling 1 m, is the kinetic energy of the plastic cart greater than, less than, or equal to the kinetic energy of the lead cart? Explain.
A g particle at is moving at m/s in the direction. As it moves, it experiences a force given by . What is the particle鈥檚 speed when it reaches m?
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