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Physics Exam ll

Terms in this set (26)

A graph depicts force versus position. What represents the work done by the force over the given displacement?
The work done is equal to the area under the curve.
If the net work done on an object is zero, what can you determine about the object's kinetic energy?
The object's kinetic energy remains the same.
If the net work done on an object is positive, what can you conclude about the object's motion?
The object is speeding up.
A person applies a 50 N force on a crate, causing it to move horizontally at a constant speed through a distance of 10 m. What is the net work done on the crate?
The net work done on the crate is zero joules.
A ball is thrown straight upward. How does the sign of the work done by gravity while the ball is traveling upward compare with the sign of the work done by gravity while the ball is traveling downward?
Work done by gravity is negative while the ball is traveling upward and positive while the ball is traveling downward.
Two objects are moving at equal speed along a level, frictionless surface. The second object has twice the mass of the first object. They both slide up the same frictionless incline plane. Which object rises to a greater height?
The two objects rise to the same height.
Two identical balls are thrown vertically upward. The second ball is thrown with an initial speed that is twice that of the first ball. How does the maximum height of the two balls compare?
The maximum height of the second ball is four times that of the first ball.
The work-energy theorem states that a force acting on a particle as it moves over a ______ changes the ______ energy of the particle if the force has a component parallel to the motion.
distance / kinetic

Kf = Ki + W
To calculate the change in energy, you must know the force as a function of _______. The work done by the force causes the energy change.
distance
Mechanical Energy
-can be dissipated to nonmechanical forms of energy.
-total mechanical energy of a system is constant only if conservative forces act.
Two men, Joel and Jerry, push against a wall. Jerry stops after 10 min, while Joel is able to push for 5.0 min longer. Compare the work they do.
Neither of them does any work.
A 3.00-kg ball swings rapidly in a complete vertical circle of radius 2.00 m by a light string that is fixed at one end. The ball moves so fast that the string is always taut and perpendicular to the velocity of the ball. As the ball swings from its lowest point to its highest point
the work done on it by gravity is -118 J and the work done on it by the tension in the string is zero
If a force always acts perpendicular to an object's direction of motion, that force cannot change the object's kinetic energy.
True
Two objects, one of mass m and the other of mass 2m, are dropped from the top of a building. When they hit the ground
the heavier one will have twice the kinetic energy of the lighter one
impulse of the force in a graph of force versus time
The impulse is equal to the area under the curve
First, you allow the brick to slam into a secured piece of wood, bringing the brick to a sudden stop. Second, you allow the brick to plow into a large slab of gelatin so that the brick comes to a gradual halt. In which situation is there a greater impulse of the force on the brick?
The impulse is the same in both situations
A lump of putty and a rubber ball have equal mass. Both are thrown with equal speed against a wall. The putty sticks to the wall. The ball bounces back at nearly the same speed with which it hit the wall. Which object experiences the greater momentum change?
The ball experiences the greater momentum change
The total momentum of an isolated system is _______.
constant
The vector sum of forces acting on a particle equals __________________.
the rate of change of momentum of the particle with respect to time
The total momentum of any number of particles is _____________.
equal to the vector sum of the momenta of the individual particles
Work
-transfer of energy on a system
-K=1/2mv^2
-Work Energy Thm:
W(net) = Change in K
-W(net) = integral(F(net)*dS)
Gravitation Potential Energy (Ug)
-energy due to an objects height (y)
-Ug = mgy
Elastic Potential Energy (Ue)
-energy due to compression/stretching of a spring
-Ue = 1/2Kx^2
Kinetic Energy
-energy of motion
- K=1/2mv^2
Work done by a Constant Force
W = Fcos(theta)(change in x)
Conservative of Forces
-do not depend on path
-if you can draw a closed loop that has an overall force of zero
-non-examples: friction & gravity
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