Physics 5B
A pendulum with a mass of 3.0 kg is released from a height of 4.4 m above the height of its resting position. How fast will the pendulum be moving when it passes through the lowest point of its swing?
9.3 m/s
A 3.00 kg toy falls from a height of 1.00 m. What will the kinetic energy of the toy be just before the toy hits the ground? (Assume no air resistance and g=9.81 m/s^2)
EPE=mgh --> 29.4 J
A small jet engine develops 1.1x10^2 N of thrust to move an airplane forward at a speed of 9.3km/h. What is the power output of the engine in watts? (1 km/h = 0.278m/s)
Eqn - P=Fv Convert - (9.3 km/h)(0.278 m/s)=2.585 m/s P = (1.1x10^2)(2.585) = 284 W
Which of the following is not a unit of power?
Joule (J)
Why doesn't the principle of mechanical energy conservation hold in situations when frictional forces are present?
Kinetic energy is not completely converted to a form of potential energy.
How much power is required to lift a 2.0 kg mass at a speed of 1.5 m/s?
P=Fv --> P=mav --> P=(2.0)(9.81)(1.5) --> Power = 29.4 Watts
Which of the following is the rate at which energy is transferred?
Power
Which of the following is the rate at which work is done?
Power
Which of the following is a true statement about the conservation of energy?
Total mass-energy is always conserved
What is the average power supplied by a 60.0 kg person running up a flight of stairs a vertical distance of 4.0 m in 4.21 s. ?
W = mgh = (60.0)(9.81)(4.0) = 2352 J P = w/t = 2352/4.21 = 560 Watts
For which of the following situations is the conservation of mechanical energy most likely to be a valid assumption?
a cannonball flies through the air
Which of the following has the greatest power output?
a crane that lifts 2.5x10^4 N beam at a speed of 1.2 m/s
Which of the following is a form of mechanical energy?
gravitational potential energy
Which of the following refers to the sum of kinetic energy and all forms of potential energy?
mechanical energy
Friction converts kinetic energy to
non-mechanical energy
In the presence of frictional force,
non-mechanical energy is no longer negligible and mechanical energy is no longer conserved.
A more powerful motor should do
the same work in a shorter time interval
