Four student helpers push carts filled with textbooks. Each cart has the same mass, 25 kg. Each student pushes the cart with a different amount of force. Which cart has the least change in speed?

Astudent in a science lab is investigating heat transfer and thermal energy conservation as she mixes hot and cold water.she first measures out her desired amount of cold water into a styrofoam cup. she then measures out hot water from the faucet or from a pot hot water on her stove. after she measures the temperature of the hot and cold waters, she pours the hot water into the cold water. she monitors the temperature of the mixed waters and records the final temperature. she uses a standard thermometer to record the temperatures. she does three trials, which are shown below: