PHYS 1044 FINAL
A woman is balancing on a high wire which is tightly strung, as shown in Fig. 9-45. The tension in the wire is
much more than the woman's weight.
An object at rest begins to rotate with a constant angular acceleration. If this object rotates through an angle θ in time t, through what angle did it rotate in the time (1/2)t?
(1/4) θ
The diving board shown here is held by two supports at A and B. Which statement is true about the forces exerted on the diving board at A and B?
FA is down, FB is up, and FB is larger than FA .
If , is V necessarily greater than V1 and/or V2?
False
It is possible to do work on an object that remains at rest
false
Kinetic energy can be negative.
false
If the net force on a system is zero, the net torque is also zero.
False
If the net torque on a system is zero, the net force is also zero.
False
One car travels due east at 40 km/h, and a second car travels north at 40 km/h. Are their velocies equal?
False
In which of the following cases does a car have a negative velocity and a positive acceleration? A car that is traveling in the
-x direction decreasing in speed.
A car traveling at a velocity v can stop in a minimum distance d. What would be the car's minimum stopping distance if it were traveling at a velocity of 2v?
4d
If μs = 0.40 and mg = 20 N, what minimum force F will keep the box from falling:
50 N;
A 60-kg woman stands on the very end of a uniform board, of length l, which is supported one-quarter of the way from one end and is balanced (Fig. 9-41). What is the mass of the board?
60 kg.
A ball is thrown straight up. What are the velocity and acceleration of the ball at the highest point in its path?
A ball is thrown straight up. What are the velocity and acceleration of the ball at the highest point in its path?
Consider a force F = 80 N applied to a beam as shown in Fig. 8-37. The length of the beam is l = 5.0 m, and θ = 37°, so that x = 3.0 m and y = 4.0 m. Of the following expressions, which ones give the correct torque produced by the force around point P?
-(80 N)(5.0 m)(sin 37°). -(80 N)(3.0 m). -(48 N)(5.0 m).
Which of the following should be part of solving any problem in physics? Select all that apply:
-Read the problem carefully. -Draw a picture of the situation. -Write down the variables that are given. -Think about which physics principles to apply. -Determine which equation can be used to apply the correct physics principles. -Calculate the solution and round it to the appropriate number of significant figures. Check the units when you have completed your calculation. -Consider whether your answer is reasonable.
You are trying to push your stalled car. Although you apply a horizontal force of 400 N to the car, it doesn't budge, and neither do you. Which force(s) must also have a magnitude of 400 N?
-The force exerted by the car on you. -The friction force exerted by the car on the road. -increases but the rope always sags where the pack hangs.
The normal force on an extreme skier descending a very steep slope (Fig. 4-42) can be zero if
-he leaves the slope (no longer touches the snow). -the slope is vertical (90°).
Which of the following forces are conservative forces:
-the force of gravity -elastic force of a spring -only if it starts moving.
Suppose you lift a suitcase from the oor to a table. The work you do on the suitcase depends on which of the following:
-the height of the table -the weight of the suitcase
Four students use dierent instruments to measure the length of the same pen. Which measurement implies the greatest precision?
160.0 mm.
The number 0.0078 has how many signicant gures?
2
A rubber band is stretched by 1.0 cm when a force of 0.35 N is applied to each end. If instead a force of 0.70 N is applied to each end, estimate how far the rubber band will stretch from its unstretched length:
2.0 cm.
A 50-N crate sits on a horizontal oor where the coecient of static friction between the crate and the oor is 0.50. A 20-N force is applied to the crate acting to the right. What is the resulting static friction force acting on the crate?
20 N to the left.
How many signicant gures does 1.362 + 25.2 have?
3
A car accelerates from rest to 30 km/h. Later, on a highway it accelerates from 30 km/h to 60 km/h. Which takes more energy, going from 0 to 30, or from 30 to 60?
30 to 60 km/h.
You are adding vectors of length 20 and 40 units. Which of the following choices is a possible resultant magnitude?
37.
When the speed of your car is doubled, by what factor does its kinetic energy increase?
4
You drop a rock o a bridge. When the rock has fallen 4 m, you drop a second rock. As the two rocks continue to fall, what happens to their velocities?
Both increase at the same rate.
As you increase the force that you apply while pulling on a rope, which of the following is NOT aected?
The Young's modulus of the rope.
In archery, how should the arrow be aimed at the target?
Above the target
Two balls are thrown o a building with the same speed, one straight up and one at a 45° angle. Which statement is true if air resistance can be ignored?
Both hit the ground with the same speed.
When a skier skis down a hill, the normal force exerted on the skier by the hill is
less than the weight of the skier.
A ball is thrown straight up. At what point does the ball have the most energy? Ignore air resistance.
Everywhere; the energy of the ball is the same at all of these points.
A heavy ball suspended by a cable is pulled to the side by a horizontal force as shown in Fig. 9-43. If angle θ is small, the magnitude of the force F can be less than the weight of the ball because:
F is equal to only the x component of the tension in the cable.
Two forces (FB = 20 N and FA = 30 N) are applied to a meter stick which can rotate about its left end, Fig. 8-15 (in textbook). Force FB is applied perpendicularly at the mid- point. Which force exerts the greater torque: FA , FB , or both the same?
FA
A parking garage is designed for two levels of cars. To make more money, the owner decides to double the size of the garage in each dimension (length, width, and number of levels). For the support columns to hold up four oors instead of two, how should he change the columns' diameter?
Increase the area of the columns by a factor of 8 by increasing their diameter by a factor of 2 square root 2
Which is not true about an order-of-magnitude estimation?
It will always be accurate to at least two signicant gures.
A truck is traveling horizontally to the right (Fig. 4-38). When the truck starts to slow down, the crate on the (frictionless) truck bed starts to slide. In what direction could the net force be on the crate?
No direcon. The net force is zero.
A satellite in circular orbit around the Earth moves at constant speed. This orbit is maintained by the force of gravity between the Earth and the satellite, yet no work is done on the satellite. How is this possible?
No work is done if the direction of motion is perpendicular to the force.
One ball is dropped vertically from a window. At the same instant, a second ball is thrown horizontally from the same window. Which ball has the greater speed at ground level?
One ball is dropped vertically from a window. At the same instant, a second ball is thrown horizontally from the same window. Which ball has the greater speed at ground level?
Ignore air resistance. As a freely falling object speeds up, what is happening to its acceleraon? does it increase, decrease, or stay the same?
Stay the same
A ball is dropped from the top of a tall building. At the same instant, a second ball is thrown upward from the ground level. When the two balls pass one another, one on the way up, the other on the way down, compare the magnitudes of their acceleration:
The acceleraon of both balls is the same.
Which statements are not valid for a projectile? Take up as positive.
The acceleration of the projectile is positive and decreasing when the projectile is moving upwards, zero at the top, and increasingly negative as the projectile descends.
A hunter is aiming horizontally at a monkey who is sitting in a tree. The monkey is so terrified when it sees the gun that it falls off the tree. At that very instant, the hunter pulls the trigger. What will happen?
The bullet will hit the monkey because both the monkey and the bullet are falling downward at the same rate due to gravity.
You push a heavy crate down a ramp at a constant velocity. Only four forces act on the crate. Which force does the greatest magnitude of work on the crate?
The force of friction.
A golf ball is hit with a golf club. While the ball ies through the air, which forces act on the ball? Neglect air resistance.
The force of gravity acting on the ball.
What causes the boat in Fig. 4-41 to move forward?
The force the water exerts on the paddle.
Two spheres have the same radius and equal mass. One sphere is solid, and the other is hollow and made of a denser material. Which one has the bigger moment of inertia about an axis through its center?
The hollow one
A ball is thrown straight up. Neglecting air resistance, which statement is NOT true regarding the energy of the ball?
The potential energy decreases while the ball is going up.
A 10.0-N weight is suspended by two cords as shown in Fig. 9-44. What can you say about the tension in the two cords?
The tension in cord A is greater than that in cord B.
A projectile is launched at an upward angle of 30° to the horizontal with a speed of 30 m/s. Is the horizontal component of its velocity 1.0 s after launch compare with its horizontal component of velocity 2.0 s after launch the same? ignoring air resistance.
True
For an answer to be complete, the units need to be specified.
True
Two steel wires have the same length and are under the same tension. But wire A has twice the diameter of wire B. Which of the following is true?
Wire B stretches four times as much as wire A.
A car travels along the x axis with increasing speed. We don't know if to the left or the right. Which of the graphs in Fig. 2-34 most closely represents the motion of the car?
a
Which of the three kicks in Fig. 3-32 is in the air for the longest time? They all reach the same maximum height h. Ignore air resistance.
all the same time
A baseball player hits a ball that soars high into the air. After the ball has left the bat, and while it is traveling upward (at point P in Fig. 3-31), what is the direction of acceleration? Ignore air resistance.
b-Assuming that we ignore air resistance, the ball is in free fall aer it leaves the bat
The solid dot shown in Fig. 8-36 is a pivot point. The board can rotate about the pivot. Which force shown exerts the largest magnitude torque on the board?
c
A skier starts from rest at the top of each of the hills shown in Fig. 6-34. On which hill will the skier have the highest speed at the bottom if we ignore friction:
c and d equally
When you apply the torque equation ∑τ = 0 to an object in equilibrium, the axis about which torques are calculated
can be located anywhere.
Suppose an object is accelerated by a force of 100 N. Suddenly a second force of 100 N in the opposite direction is exerted on the object, so that the forces cancel. The object
continues at the velocity it had before the second force was applied
Bonnie sits on the outer rim of a merry-go-round, and Jill sits midway between the center and the rim. The merry-go-round makes one complete revolution every 2 seconds. Jill's linear velocity is:
half of Bonnie's.
Accuracy represents
how close a measurement is to the true value.
You are riding in an enclosed train car moving at 90 km/h. If you throw a baseball straight up, where will the baseball land?
in your hand
A person stands on a scale in an elevator. His apparent weight will be the greatest when the elevator
is accelerating upward.
A man pushes a block up an incline at a constant speed. As the block moves up the incline,
its potential energy increases and its kinetic energy remains the same.
A car travels 10 m/s east. Another car travels 10 m/s north. The relative speed of the first car with respect to the second is
less than 20 m/s.
To pull an old stump out of the ground, you and a friend tie two ropes to the stump. You pull on it with a force of 500 N to the north while your friend pulls with a force of 450 N to the northwest. The total force from the two ropes is
less than 950 N.
A uniform beam is hinged at one end and held in a horizontal position by a cable, as shown in Fig. 9-42. The tension in the cable
must be at least half the weight of the beam, no maer what the angle of the cable.
A 10.0-kg box is dragged on a horizontal frictionless surface by a horizontal force of 10.0 N. If the applied force is doubled, the normal force on the box will
remain the same;
Two children are balanced on opposite sides of a seesaw. If one child leans inward toward the pivot point, her side will
rise.
Does a car speedometer measure speed, velocity, or both?
speed
Figure 2-31 shows the velocity as a function of time for two cars accelerating from 0 to 100 km/h in a time of 10.0 s. Compare the average acceleration:
the average acceleration of car A is the same as car B.
During baseball pracce, a player hits a very high fly ball and then runs in a straight line and catches it. Which had the greater displacement, the player or the ball?
the displacement of both was the same.
You are pushing a heavy box across a rough oor. When you are initially pushing the box and it is accelerating,
the force you exert on the box is equal to the force of the box pushing back on you.
A baseball is hit high and far. Which of the following statements is true? At the highest point,
the magnitude of the velocity is the slowest.
A uniform meter stick supported at the 25-cm mark is in equilibrium when a 1-kg rock is suspended at the 0-cm end (as shown in Fig. 9-37). Is the mass of the meter stick greater than, equal to, or less than the mass of the rock? Explain your reasoning.
the mass of the meter stick is equal to the Rock.
A small force can exert a greater torque than a larger force.
true
An object can be increasing in speed as its acceleration decreases
true
An object can have zero acceleraon and nonzero velocity at the same me.
true
Potenal energy can somemes be negave.
true
The velocity of an object can be negave when its acceleraon is positive
true
If you push on a heavy desk, does it always push back on you? Points: 3
yes