Power/ Machines
_______ is defined as the rate at which work is done.
Power
The transfer of energy to a body by the application of a force that causes the body to move in the direction of the force is called
Work
A boy exerts an average force of 60 N when he lifts a box 1.5 meters. How much work does he do?W=FxD
Work=90J
What is the value of free-fall acceleration (gravity) on Earth?
9.8 m/s²
The energy of position is called _______
Potential energy
What are the two families of simple machines?
inclined plane and lever
units for work are
Joules
What is the mechanical advantage of a ramp 4.0 m long and 0.80 m tall?
MA = input distance / output distance
Mechanical Advantage=5
Work = Force x _________
distance
What is the energy of motion called?
Kinetic Energy
Levers are divided into how many classes based on the location of the fulcrum and of the input and output forces?
3
Lifting a car using a car jack is considered easier because you use ____ _____.
Less force
A 35 kg object is lifted 9 m from the floor to the table. What is the object's gravitational potential energy?
PE=mgh
3087J
How much power is required to do 140 J of work in 4.2 s?
P=W/t
Power=33.33W
We define the total mechanical energy of an object as _____+______
potential energy + kinetic energy
A wedge is a modified form of which simple machine?
inclined plane
The force you exert when you use a machine is the ________.
Input force
An object of mass 6 kg has a speed of 12 m/s and moves a distance of 8 m. What is its kinetic energy?
KE= ½ mv2
432J
What is the mechanical advantage of a pulley lifting a bucket weighing 265 N when the person is putting 75 N of force?
Mechanical Advantage=3.533
Where is the potential energy of a pendulum least?
a) at the bottom of the swing
b) at the top of the swing
c) in the middle of the swing
At the bottom of its swing
A ramp is a simple inclined plane that allows one to apply an input force that is _____ the output force.
less than
The force exerted by the machine is the ________.
Output force
What is the equation for Potential Energy?
Potential Energy = mass X gravity X height
What is the equation for Kinetic Energy?
KE= ½ mv2
As a dropped penny falls toward the ground, ______ energy is converted to ______ energy.
potential, kinetic