A thermostat is a switch that operates itself when the temperature goes above or below a temperature that the user can set.
-- Before you go to bed, you set the thermostat for 65° . If the temperature in the house goes below 65° during the night, the thermostat turns on the furnace, and keeps it running until the house warms up to 65°. Then it shuts the furnace off.
-- After breakfast, you set the thermostat for 75°. If the temperature in the house goes above 75°, during the day, the thermostat turns on the air conditioner, and keeps it running until the house cools down to 75°. Then it shuts the air conditioner off.
-- On Sunday morning, you put the slow cooker on the kitchen counter, and you throw in a big roast, a sliced onion, some baby carrots, some sliced potatoes, some vegetable stock, salt, pepper, garlic, chili powder, and tomato paste. Then you put the cover on, turn the power on, and set the slow cooker to "LOW". The heater in the slow cooker turns on. Whenever the temperature in the crock gets higher than 160°, the thermostat in the slow cooker turns off the heater, and keeps it off until the crock cools down to 160°. Then the thermostat turns the heater on again. By dinner time, you have a hot, juicy, scrumptious pot roast, ready to eat. It's not too hot, not too cold, not too tough, not dried out, and it melts in your mouth. You're still thinking about it when you go to bed, and your mom gives you a slice to take to school for your lunch on Monday.
It's a physical event that happens where an object is thrown in free air (no friction) forming an angle with the horizontal reference. The object then describes a path called a parabola.
The object will reach its maximum height and then return to the height from which it was launched. The equation for the height is
:
Where vo is the initial speed, is the angle, t is the time and g is the acceleration of gravity
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In this problem we'll assume the arrow was launched from the ground level (won't consider the archer's height). Thus , and:
The value of y is zero twice: when t=0 (at launching time) and in t= when it goes back to the ground. We need to find that time by making