Misconceptual Questions PHY 201
Answer skier question assuming a small amount of friction
C (tallest and steepest one)
An ideal gas undergoes an isothermal process. Which of the following statements are true? (i) No heat is added to or removed from the gas. (ii) The internal energy of the gas does not change. (iii) The average kinetic energy of the molecules does not change.
(ii) and (iii) only
Which of the following possibilities could increase the efficiency of a heat engine or an internal combustion engine?
- Increase the temperature of the hot part of the system and reduce the temperature of the exhaust - Decrease the temperatures of both the hot part and the exhaust part of the system by the same amount
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 equations can be used to apply the correct physics principles - Check the units when you have completed your calculation - Consider whether or not your answer is reasonable
Which of the 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. - The velocity at the highest point is zero
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 ball is thrown downward at a speed of 20 m/s. Choosing the + y-axis pointing up and neglecting air resistance, which equations could be used to solve for other variables? The acceleration due to gravity is g = 9.8 m/s2 down.
- y = y0+(-20 m/s)t - (1/2)gt2 - v2 = (20 m/s)2 - 2g(y-y0)
You are in the middle of a large field. You walk in a straight line for 100 m, then turn left and walk 100 m more in a straight line before stopping. When you stop, you are 100 m from your starting point. By how many degrees did you turn?
120 degrees
About what percentage of the heat produced by burning gasoline is turned into useful work by a typical automobile?
20%
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
A car traveling at a velocity (v) can stop at a minimum distance (d). What would be the car's minimum stopping distance if it were traveling at a velocity of 2v?
4d
A heat engine operates between a high-temperature of about 600 degrees C and a low temperature of about 300 degrees C. What is the maximum theoretical efficiency for this engine?
About 34%
Which of the three kicks is in the air for the longest time? They all reach the same maximum height. Ignore air resistance.
All at the same time
A bullet fired from a rifle begins to fall
As soon as it leaves the barrel
Which is possible: converting (i) 100 J of work entirely into 100 J of heat, (ii) 100 J of heat entirely into 100 J of work?
Both (i) and (ii) are possible
A skier starts from rest at the top of each of the hills shown in the figure. On which hill will the skier have the highest speed at the bottom if we ignore friction?
Both C and D (the tallest ones)
You drop a rock off 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
An ideal gas undergoes an adiabatic expansion, a process in which no heat flows into or out of the gas. As a result,
Both the temperature and pressure of the gas decrease
Two balls are thrown off a building with the same speed, one straight up and one at a 45-degree angle. Which statement is true if air resistance.
Both will hit the ground at the same time
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 the figures most closely represents the motion of the car?
Concave down
A small boat coasts at a constant speed under a bridge onto the boat. The speed of the boat:
Decreases
Which statement is true regarding the entropy change of an ice cube that melts?
Entropy increases
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
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 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
You drive 4 km at 30 km/h and then another 4 km at 50 km/h. What is your average speed for the whole 8-km trip?
Less than 40 km/h
The magnitude of a component of a vector must be:
Less than or equal to the magnitude of the vector
A railroad tank car contains milk and rolls at a constant speed along a level track. The milk begins to leak out the bottom. The car then...
Maintains a constant speed
Two identical billiard balls traveling at the same speed have a head-on collision and rebound. If the balls had twice the mass but maintained the same size and speed, how would the rebound be different?
No difference
A bowling ball is dropped from a height (h) onto the center of a trampoline, which launches the ball back up into the air. How high will the ball rise?
No more than h - probably a little less
A satellite in a circular orbit around the Earth moves at a 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
On a very hot day, could you cool your kitchen by leaving the refrigerator door open?
No, the heat exhausted by the refrigerator into the room is more than the heat the refrigerator takes out of the room.
You push very hard on a heavy desk, trying to move it. You do work on the desk:
Only if it starts moving
A space vehicle, in a circular orbit around the earth, collides with a small asteroid which ends up in the vehicle's storage bay. For this collision,
Only momentum is conserved
An ideal gas undergoes an isothermal expansion from state A to state B. In this process...
Q > 0, U = 0, W > 0
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, what is the direction of acceleration? Ignore air resistance.
Straight down
A ball is dropped from the top of a tall building. At the same instant, a second ball is thrown upward from 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 acceleration of both balls is at the same speed
A baseball is pitched horizontally toward home plate with a velocity of 110 km/h. In which of the following scenarios does the change in momentum of the baseball have the largest magnitude?
The ball is popped straight up at a speed of 110 km/h
A bowling ball hangs from a 1.0 m long cord, (i) A 200 g putty ball moving 5.0 m/s hits the bowling ball and sticks to it, causing the bowling ball to swing up; (ii) A 200 g rubber ball moving 5.0 m/s hits the bowling ball and bounces straight back at nearly 5.0 m/s, causing the bowling ball to swing up. Describe what happens.
The ball swings up farther in (ii) than in (i)
You are lying in bed and want to shut your bedroom floor. You have a bouncy ball and a blob of clay, both with the same mass. Which one would be more effective to throw at your door to close it?
The bouncy ball
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 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 and an equal-mass bean bag are dropped from the same height and hit the ground. The bean bag stays on the ground while the golf ball rebounds. Which experiences the greater impulse from the ground?
The golf ball
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
At time t = 0 an object is traveling to the right along the +x axis at a speed of 10.0 m/s with acceleration -2.0 m/s2. Which statement is true?
The object will slow down, momentarily stopping, then pick up speed moving to the left
A ball is thrown straight up. Neglecting air resistance, which statement is not true regarding the energy of the ball?
The potential energy decreases when the ball is going up
Engines, including car engines, are rated at horsepower. What is horsepower?
The rate at which the engine can do work
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?
The thrown ball
An ideal gas undergoes an isobaric compression and then an isovolumetric process that brings it back to its initial temperature. Had the gas undergone one isothermal process instead,
The work done on the gas would be greater
A small car and heavy pickup truck are both out of gas. The truck has twice the mass of the car. After you push first the car and then the truck for the same amount of time with the same force, what can you say about the momentum and kinetic energy (KE) of the car and the truck? Ignore friction.
They both have the same KE, but the truck has more momentum than the car
Answer the car and truck question assuming that you push both the car and the truck for the same distance with the same force.
They both have the same KE, but the truck has more momentum than the car
A truck going 15 km/h has a head-on collision with a small car going 30 km/h. Which statement best describes the situation?
They both have the same change in the magnitude of momentum because momentum is conserved
An astronaut is a short distance away from her space station without a tether rope. She has a large wrench. What should she do with the wrench to move toward the space station?
Throw it directly away from the space station
A ball is thrown straight up. What are the velocity and acceleration of the ball at the highest point in its path?
V = 0, a = 9.8 m/s2 down
In an isobaric compression of an ideal gas,
Work is done on the gas