Three people pull simultaneously on a stubborn donkey. jack pulls directly ahead of the donkey with a force of 63.9 n63.9 n , jill pulls with 79.1 n79.1 n in a direction 45° to the left, and jane pulls in a direction 45° to the right with 183 n183 n . (since the donkey is involved with such uncoordinated people, who can blame it for being stubborn? ) find the magnitude of the net force the people exert on the donkey.

The energy released by a chemical reaction can be measured using a calorimeter. when barium hydroxide octahydrate crystals are reacted with dry ammonium chloride inside of a coffee cup calorimeter, the temperature of the 18.00 g of water in the calorimeter decreases from 30.0°c to 8.0°c. the equation for calculating energy absorbed or released by a reaction is: where q is the energy released or absorbed, m is the mass of water in the calorimeter, cp is the specific heat of water, and δt is the observed temperature change. if the specific heat of liquid water is 4.19 j/g·°c, how much energy was absorbed by the reaction?

1. jay fills a wagon with sand (about 20 kg) and pulls it with a rope 30 m along the beach. he holds the rope 25° above the horizontal. the rope exerts a 20-n tension force on the wagon. how much work does the rope do on the wagon?

What is the kinetic energy of a baseball moving at a speed of 40 m/s if the baseball has mass of 0.15 kg?