An ice skater at rest on ice catches a dance partner moving 2.5 m/s during a performance. The ice skater has a mass of 68 kg and the dance partner has a mass of 54 kg. What is the speed of the ice skater and dancer partner after the collision?
A) 2.3 m/s
B) 2.0 m/s
C) 1.4 m/s
D) 1.1 m/s
A machine works with an efficiency of 18%. The energy input is 500 joules/second. How much useful energy will the machine generate in 15 minutes?
A) 81 kg
B) 1.35 kg
C) 25 kg
D) 135 kg
A lever is being used to try to lift a heavy object but it is not working. Which of these actions would increase the output force the most?
A) decrease the input force and increase the output displacement
B) increase the input force and decrease the output displacement
C) decrease the input force and decrease the output displacement
D) increase the input force and increase the output displacement