physics pt 3 hoe
A force F at an angle θ above the horizontal is used to pull a heavy suitcase of weight mg a distance d along a level floor at constant velocity.The coefficient of friction between the floor and the suitcase is . The work done by the frictional force is:
-Fd cos θ
The resultant force on an object over a 0.50-s time interval is plotted against the objects displacement in the graph below. How much work did this force do on the object during the 0.50-s interval?
0 J
The path of a 2 kg pendulum bob moving to and fro is shown in the diagram below. Frictional forces can be assumed to be negligible. What is the height of the pendulum bob at point A?
0.51 m
A marble rolls along the track below with no friction. The sequence of positions on the track listed in order from the lowest kinetic energy to the highest kinetic energy is:
1, 5, 4, 2, 3, 6
A rock of mass m is thrown horizontally off a building from a height h, as shown above. The speed of the rock as it leaves the thrower's hand at the edge of the building is v0. What is the kinetic energy of the rock just before it hits the ground?
1/2mv^2+mgh
The height to which a 50-kilogram object must be lifted to increase its potential energy by 5,000 joules is about:
10 meters
A force acts on an object, causing it to move parallel to the force. The graph in the figure shows this force as a function of the position of the object. How much work does the force do as the object moves from 0 to 15 m?
125 J
Jeff, a snowboarder who's mass is 102 kilograms, is practicing on a trampoline for an upcoming competition. As Jeff bounces straight up off the trampoline, his speed is 6.26 m/sec. When he reaches the top of his bounce, his potential energy is approximately:
2,000 joules.
The path of a 2 kg pendulum bob moving to and fro is shown in the diagram below. Frictional forces can be assumed to be negligible. What is the pendulum bob's velocity at point B?
2.8 m/s
An object with a mass of 10 kg is initially at rest at the top of a frictionless inclined plane that rises at 30° above the horizontal. At the top, the object is initially 8.0 m from the bottom of the incline, as shown in the figure. When the object is released from this position, it eventually stops at a distance d from the bottom of the inclined plane along a horizontal surface, as shown. The coefficient of kinetic friction between the horizontal surface and the object is 0.20, and air resistance is negligible. Find the distance d.
20 m
The figure shows a famous roller coaster ride. You can ignore friction. If the roller coaster leaves point Q from rest, what is its speed at the top of the 25-m peak (point S)?
22 m/s
A 60-kg skier starts from rest from the top of a 50-m high slope. If the work done by friction is -6000 J, what is the speed of the skier on reaching the bottom of the slope?
28 m/s
Consider the following situation: A skier is pulled by a toe rope from the bottom of a training hill (initial state) to the top of the training hill (final state) at a constant speed. Which work-energy bar chart below best describes this situation?
2K + 4W = 2K + 4P
The kinetic energy of a go-cart with a mass of 150 kilograms and a speed of 20.0 m/sec is:
30,000 joules.
A 1000-kg car experiences a net force of 9500 N while slowing down from 30 m/s to 15.9m/s How far does it travel while slowing down?
34 m
A bead is moving with a speed of 20 m/s at position A on the track shown in the figure. This track is friction-free, and there is no appreciable air resistance. What is the speed of the bead at point C?
34 m/s
A 3.0 kg stone is dropped from a height of 10 m and strikes the ground with a speed of 13 m/s. What average force of air friction acted on the stone as it fell?
4.1 N
In the figure, a ball hangs by a very light string. What is the minimum speed of the ball at the bottom of its swing (point B) in order for it to reach point A, which is 1.0 m above the bottom of the swing?
4.4 m/s
A ball swings freely back and forth in an arc from point I to point IV, as shown. Point II is the lowest point in the path, III is located 0.5 meter above II, and IV is I meter above II. Air resistance is negligible. The speed of the ball at point II is most nearly
4.5 m/s
Dennis Elbough pushes on a 53.5-kg box with a forward force of 300 N to move it 17.0 m across the floor. The work done by Dennis on the box is _____ J.
5100
Matthew pulls his little sister Sarah along the horizontal ground in a wagon. He exerts a force on the wagon of 60.0 N at an angle of 37.0° above the horizontal. If he pulls her a distance of 12.0 m, how much work does Matthew do?
575 J
Consider the three situations described below. In which situation would the mechanical energy be conserved?
A projectile rises upward toward the peak of its trajectory. Neglect frictional forces.
The path of a 2 kg pendulum bob moving to and fro is shown in the diagram below. Frictional forces can be assumed to be negligible. Which of the following energy bar charts best describes the energy state of the pendulum at point C?
All KE and all TME
A ball swings freely back and forth in an arc from point I to point IV, as shown. Point II is the lowest point in the path, III is located 0.5 meter above II, and IV is I meter above II. Air resistance is negligible. If the potential energy is zero at point II, where will the kinetic and potential energies of the ball be equal?
At point III
Some forces are categorized as conservative forces (or internal forces) while others are categorized as non-conservative forces (or external forces). Which of the following forces are generally categorized as conservative (or internal) forces?
Gravity Force
Two frisky otters slide down frictionless hillsides of the same height but different slopes. The slope of the hill of otter 1 is 30°, while the slope of the hill of otter 2 is 60°. If both start from rest, which otter is moving faster when she reaches the bottom of her hill?
Otter 2 is moving faster.
Two identical balls roll down two hills having different incline angles. Upon which hill will the ball be traveling fastest when it reaches the bottom? The balls each start from rest at the same height. Ignore all frictional forces.
Same speed at bottom of both hills
A moving car has kinetic energy. To bring the car to rest, you must decrease its kinetic energy to zero. The brakes do this work by applying a force over a distance. What effect would doubling the speed have on the braking distance?
The braking distance would be 4 times greater.
Which statement is always true of an object that has kinetic energy?
The object is moving.
Which of the following changes would cause the kinetic energy of an object to increase?
The speed of the object increases.
A girl throws a stone from a bridge. Consider the following ways she might throw the stone. The speed of the stone as it leaves her hand is the same in each case.Case A: Thrown straight up.Case B: Thrown straight down.Case C: Thrown out at an angle of 45° above horizontal.Case D: Thrown straight out horizontally.In which case will the speed of the stone be greatest when it hits the water below if there is no significant air resistance?
The speed will be the same in all cases.
A ball starts from rest on top of a tall pillar and falls to the ground below. Assume the effect of air resistance is negligible. which of the following terms in the Conservation of Energy equation can be cancled?
Wnc
A football is kicked off the ground a distance of 50 yards downfield. Neglecting air resistance, which of the following statements would be INCORRECT when the football reaches the highest point?
all of the balls original kinetic energy has been changed into potential energy
The brakes on an automobile become hot when they are used continuously because the:
friction is a non-conservative force and can change TME.
f an object has energy, then one can be certain that it ____.
has the ability to do work on another object
A rolling wagon has 50 joules of kinetic energy. If the wagon's velocity is doubled, the kinetic energy of the wagon:
is increased to 200 joules.
Of the following examples, the one that represents work as defined by a scientist is:
lifting a book from your desk.
A softball player catches a ball of mass m, which is moving towards her with horizontal speed v. While bringing the ball to rest, her hand moved back a distance d. Assuming constant deceleration, the horizontal force exerted on the ball by the hand is
mv^2/(2d)
Swimmers at a water park have a choice of two frictionless water slides, as shown in the figure. Although both slides drop over the same height h, slide 1 is straight while slide 2 is curved, dropping quickly at first and then leveling out. How does the speed v1 of a swimmer reaching the bottom of slide 1 compare with v2, the speed of a swimmer reaching the end of slide 2?
v1 = v2
When you throw a pebble straight up with initial speed V, it reaches a maximum height H with no air resistance. At what speed should you throw it up vertically so it will go twice as high?
√2V
