Work and Energy Review
If the mass in a horizontal mass-spring system was doubled, the elastic potential energy in the system would change by a factor of
0 (no change)
A horizontal force of 10N is used to pull a 5 kg block across a floor at a constant speed of 3 m/s. There is a frictional force of 10 N also acting on the block. What is the net work done on the block?
0 J
A 5.0-kg object slides down a surface inclined at an angle of 30o from the horizontal. Friction may be neglected. The total distance moved by the object along the plane is 10 meters. The work done on the object by the normal force exerted on the object by the surface is most nearly _____.
0 KJ
If the displacement of a horizontal mass-spring system was doubled, the elastic potential energy in the system would change by a factor of
4
An arrow is drawn back so that 50 joules of potential energy is stored in the stretched bow and string. When released, the arrow will have a kinetic energy of ______ Joules.
50
An object on which a variable force is exerted travels a distance of 20 m in a straight line in the same direction as the force. The graph shows the force exerted on the object as a function of the position. What was the total force on the object during the full 20 m trip?
60 J
During a pull-up, a 90kg man raises himself by 80cm. The work done in a single pull-up is most nearly:
706 Joules
If both the mass and the velocity of an asteroid are doubled, the kinetic energy of the asteroid is increased by a factor of:
8
When my velocity triples, my kinetic energy increases by ______ times.
9
A joule is defined as_______
A force of one newton over a distance of one meter
Which of the following is work NOT being done? (check all that apply)
A mother is holding her baby on her hip and A mother carries her baby down the hall
If mechanical work is done on an object, the object must
Accelerate
On a roller coaster, where is maximum potential energy?
At the top of a big hill
Which point has the most kinetic energy?
C
Friction removes energy from a system by...
Converting it into thermal energy
When negative work(by friction or external forces) is done on a system, the total energy will ______.
Decrease
________ is energy stored by things that stretch or compress.
Elastic potential Energy
How much farther will a car traveling 100 km/s skid than the same car traveling at 50 km/s?
Four times as far
What must be true about the component of a force in order for the force to do work on an object?
It must be parallel to the displacement of the object.
What kind of energy is in a moving skateboard?
Kinetic
As the skier goes down the hill,_________ energy increases while __________energy decreases.
Kinetic; gravitational
Which of the following energy forms is the sum of kinetic energy and all forms of potential energy?
Mechanical Energy
A small economy car (low mass) and a limousine (high mass) are pushed from rest across a parking lot, equal distances with equal forces. The car that receives more kinetic energy is
Neither one - they receive the same amount of KE
These boys are pulling with the same amount of force so they don't move.
No work is done by either boy.
Which of these Machines has the greatest power?
One that does 100 Joules of work in 50 seconds
Which of the following equations is not an equation for power, P, in terms of work, W, displacement, d, time interval, t, force, F, and/or velocity, v? (hint: look at units)
P=Fv/Δt
The potential energy of a box on a shelf, relative to the floor, is a measure of___
The work done by putting the box on the shelf, the weight of the box times the distance above the floor, and the energy because of its position above the floor. All of these :D
Choose the following sentence that incorporates the scientific meaning of work.
Tim does work Shoveling snow.
Which of the following is a true statement about the conservation of energy?
Total energy is always conserved.
What is work?
Transfer of force over a distance
The unit used to measure power is the
Watt
Which has the most kinetic energy from its motion?
a 900-kg car traveling 80 km/h
When positive work by an external force is done on a system, the energy of the system will _____.
increase
Can energy be destroyed?
no
Where in the skatepark are potential and kinetic energy of the skater roughly equal?
point c
2 balls of equal mass roll down opposite sides from the top of a frictionless hill. Regardless of the path they take, what will the velocity of the balls be when the hit the ground?
same
A variable force is represented on an F-versus-x graph. Which of the following is the work done by this force?
the area bounded by the curve and the x axis
The weight of an object on the Moon is one-sixth its weight on Earth. An object moving with a given speed on the Moon has kinetic energy equal to ______________ it would have if it were moving at the same speed on Earth.
the kinetic energy
At the bottom of the hill, the skier jumps off of a ramp. The ramp causes the skier to _____.
gain potential energy
A person on a roof throws one ball downward and an identical ball upward at the same speed. The ball thrown downward hits the ground with 140J of kinetic energy. Ignoring air friction, with how much kinetic energy does the second ball hit the ground? (Think!)
140J
In which of the following situations do your arms do work on books?
Picking up a pile of books from the floor
What kind of energy is in a rock at the edge of a cliff?
Potential
Which of the following statements is true?
Potential energy can be negative but kinetic energy cannot.
Which of the following is the rate at which energy is transferred?
Power
Which of the following parameters expresses the stiffness of a spring in regards to elastic potential energy?
Spring Constant
As the skier goes down the hill, total energy ______ (assume no friction).
Stays the same
An object moves with decreasing speed. Which of the following statements is true?
The net work done on the object is negative, and the kinetic energy is decreasing.
The reference point for gravitational potential energy
can be chosen arbitrarily.
The ability to do work is...
energy
In which of the following is no work done
there is work being done in each example (climbing stairs,lifting a book,pushing a shopping car)
