Review 1. What units would you use to describe the speed of a
car? Would you use different units for the speeds of
runners in a neighborhood race? Explain.
2. In a skateboarding marathon, the winner covered 435 km
in 36.75 h. What was the winner's average speed?
3. Think Critically: Make a distance-time graph for a
2-hour car trip. The car covered 50 km in the first
30 minutes, stopped for 30 minutes, and covered 60 km
in the final 60 minutes. Note the three graph segments.
Which graph segment slopes the most? Which one does
not slope? What was the car's average speed?

Hydrogen and helium are both members of?

As part of your daily workout, you lie on your back and push with your feet against a platform attached to two stiff springs arranged side by side so that they are parallel to each other. when you push the platform, you compress the springs. you do an amount of work of 79.0 j when you compress the springs a distance of 0.230 m from their uncompressed length. (a) what magnitude of force must you apply to hold the platform in this position? (b)how much additional work must you do to move the platform a distance 0.230 m farther? (c) what maximum force must you apply to move the platform a distance 0.230 m farther?

4r-134a enters the condenser of a residential heat pump at 800 kpa and 50°c at a rate of 0.022 kg/s and leaves at 750 kpa subcooled by 3°c. the refrigerant enters the compressor at 200 kpa superheated by 4°c determine (a) the isentropic efficiency of the compressor, (b) the rate of heat supplied to the heated room, and (c) the cop of the heat pump. also, determine (d) the cop and rate of heat supplied to the heated room if this heat pump operated on the ideal vapor-compression cycle between the pressure limits of 200 and 800 kpa. (0.757, 4.37 kw, 5.12, 6.18, 3.91 kw)