AP Physics Semester 1: Conceptual Questions

In a displacement by time graph, what type of graph would represent an object at rest?

A horizontal line BECAUSE as the time increases, the displacement stays the same.

A girl attaches a rock to a string, which she then swings counter clockwise in a horizontal circle. The string breaks at a certain point, what path will the rock follow?

A path perpendicular to the point it was released at BECAUSE ??

An object is moving with the constant non zero velocity in the +x direction. What does the position vs time graph of this object look like?

A straight line making an angle with the time axis BECAUSE as time increases, the velocity is also increasing constantly.

What does the slope of a position vs. time graph give you?

Acceleration BECAUSE the shape of the line gives you velocity but the slope tells you how much it increases by.

A rock from a volcanic eruption is launched straight up into the air with no appreciable air resistance. What is correct about the velocity and acceleration while the rock is in the air?

The acceleration is downwards in all points of motion BECAUSE after it has been thrown out of the volcano, gravity is working. Gravity is constant and down. Doesn't matter if the rock is on the way up, or the way down, it is accelerating downward due to gravity.

Suppose that a car traveling to the west begins to slow down as it approaches a traffic light. What is true about the acceleration?

The acceleration is towards the east BECAUSE it is decelerating towards the west??

If the force in an object is in the negative direction, what direction is the work it does on the object?

The work could be either positive or negative BECAUSE it depends on the direction the object moves.

Two blocks, A and B, are being pulled to the right along a horizontal surface by a horizontal by a horizontal 100 N pull. Both are moving together at a constant velocity of 2 m/s to the right and both weigh the same. What is a correct free body diagram of the horizontal forces acting on the upper block, A?

There are no horizontal forces that act on A BECAUSE B is the box experiencing a pull. There are vertical forces, however.

In an air free chamber, a pebble is thrown horizontally, and at the same instant a second pebble is dropped from the same height, what are the times of fall of the two pebbles?

They hit at the same time BECAUSE they are released from the same height with the same initial velocity.

Which of the following quantities has units of displacement?

anything with mi, km, etc NO m/s^2 or m/s BECAUSE they do not show the displacement, only the speed or acceleration you are at.

A 10 kg and a 20 kg rock are thrown upward with the same initial speed of zero and experience no significant air resistance. If the 10 kg rock reaches a maximum height h, what maximum height will the 20 kg ball reach?

h (the same height) BECAUSE mass does not matter when there is no air resistance and they are thrown with the same velocity.

A 35 N bucket of water is lifted vertically 3 m and then returned to its original position. How much work did gravity do on the bucket in this process?

0 J BECAUSE the gravity cancels out and there was no overall displacement from start to finish

The sum of two vectors of fixed magnitudes has the greatest magnitude when the angle between these two vectors is...?

0 degrees BECAUSE ??

When you drop a pebble from height H, it reaches the ground with kinetic energy K if there is no air resistance. From what height should you drop it so it will reach the ground with twice as much kinetic energy?

2H BECAUSE twice the height will give you twice the potential energy to convert to kinetic energy.

When you drop a pebble from height H, it reaches the ground with speed V if there is no air resistance. From what height should you drop it so it will reach the ground with twice as much speed?

4H BECAUSE if the speed needs to doubled the height should be quadrupled.

Which requires more work, increasing a cars speed from 0 mph to 30 mph or from 50 mph to 60 mph?

50 mph to 60 mph BECAUSE more force is required.

For general projectile motion with no air resistance, what is the horizontal component of a projectile's acceleration?

Always zero BECAUSE acceleration is not horizontal.

A child is standing on a bridge throws a rock straight down. The rock leaves the child's hand at a time t = 0 seconds. If we take upwards as the positive direction, what would that graph the best represents the velocity of the stone as a function of time look like?

An exponential curve under the x axis starting at zero BECAUSE the rock increases its velocity each second, it does not remain constant because there is an acceleration due to gravity. If there was no acceleration the velocity would remain constant and the line would not curve.

A racing car accelerates uniformly from rest along a straight track. This track has markers spaced at equal distances along it from the start. The car reaches a speed of 140 km/h as it passes marker two. Where on the track was the car when it was traveling at half this speed, that is 70 km/h?

Before marker one BECAUSE the time it takes is longer so it will reach 70 km/h much before marker one??

You and your friend, who weighs the same as you, want to go to the top of the Eiffel Tower. Your friend takes the elevator straight up. You decide to walk up the spiral staircase, taking longer to do so. What is your gravitational potential energy compared to your friends at the top?

Both of you have the same amount of gravitational potential energy at the top BECAUSE you traveled the same distances and used the same force.

In a velocity by time graph, the motion of a particle begins under the x axis and makes a straight diagonal line and continues onward until it is above the x axis, what can you say about the speed of the particle?

Decreases then increases BECAUSE the magnitude of the number is what matters, not the sign in front of it.

What would a graph that represents zero acceleration look like?

Diagonal line pointing away from the axis on a displacement vs time graph BECAUSE the velocity is constant. Also, on a velocity vs. time graph, it would be a horizontal line BECAUSE as time increases, velocity is not; once again, it is constant.

A satellite is in orbit around the earth. Which one feels the greatest force?

Earth and the satellite feel exactly the same force BECAUSE equal and opposite.

Two blocks, A and B, are being pulled to the right along a horizontal surface by a horizontal by a horizontal 100 N pull. Both are moving together at a constant velocity of 2 m/s to the right and both weigh the same. What is correct about the horizontal forces acting on the lower block, B?

Equal on both sides BECAUSE friction pushes back with the same force that you are pulling against it with. Equal and opposite.

The object of weight W is in free fall close to the surface of the Earth. What is the magnitude of the force that the object exerts on Earth?

Equal to W BECAUSE equal and opposite.

The magnitude of the resultant of two vectors cannot be less than the magnitude of either of those two vectors, true or false?

False BECAUSE ??

Jill dies twice as much work as Jack dies in half the time. What is Jill's power output?

Four times Jack's power output BECAUSE 2 divided by 1/2 is four.

Joe and Bill throw identical balls vertically upward. Joe throws his ball with an initial speed twice as high as Bill. If there is no air resistance, what will the maximum height of Joe's ball be?

Four times that of Bill's ball BECAUSE if you do the math, 2 squared is four times larger than 1 squared.

A rock is thrown from the upper edge of a tall cliff at some angle above the horizontal. It reaches its highest point and starts falling down. What is true about the vertical and horizontal components of the velocity?

Its vertical velocity component is the same as it was just as it was launched BECAUSE there is no vertical velocity; it always remains as zero. Also, its horizontal velocity component is the same as it was just as it was launched BECAUSE the horizontal component in a projectile does not change.

James and John dive from an overhang into the lake below. James simply drops straight down from the edge. John takes a running start and jumps with an initial horizontal velocity of 25 m/s. When will they each reach the lake below if there is no air resistance?

James and John will reach the surface of the lake at the same time BECAUSE they start from the same height with the same initial velocity.

You drive six km at 50 km/h and then another six km at 90 km/h. What will your average speed be?

Less than 70 km/h BECAUSE the average is 70 km/h, however, you drive less than 70 km/h for longer because you are driving slower.

Two men, Joel and Jerry, push against a car that has stalled, trying unsuccessfully to get it moving. Jerry stops after 10 minutes, while Joel is able to push for 5 more minutes. What is the difference between their work on the car?

Neither of them do any work BECAUSE the car does not move.

If the velocity of an object is zero at some point, then will the acceleration also be zero at that point?

No BECAUSE as long as the object will increase its speed in the next period of time, there will be an acceleration??

In order to get an object moving, do you need to push harder on it than it pushes back on you?

No BECAUSE equal and opposite.

A box is placed on a table which rests on the floor. The box pushes on the table; is the reaction force to the box's push on the table, the table's push on the floor?

No BECAUSE of normal force. The tables reaction is to push back on the box.

If a vectors components are all negative, then is the magnitude of the vector is negative?

No BECAUSE when the components are squared, they become positive.

Can an object have a constant non-zero velocity and a changing acceleration?

No BECAUSE when the velocity does not increase, there is no acceleration.

For general projectile motion with no air resistance, what happens to the horizontal component of a projectile's velocity?

Remains a non zero constant BECAUSE ??

Ball A is dropped from the top of a building. One second later, ball B is dropped from the same building, as time progresses, what is the difference in their speeds?

Remains constant BECAUSE they accelerate at the same rate and as the height increases, so does the velocity; they are directly proportional.

When you throw a pebble straight up with immortal 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?

Square root of 2 times V BECAUSE for the equation of kinetic energy equals potential you would multiply both sides by 2V^2 and square root it.

Bill and his daughter Susan are both standing on identical skateboards, initially at rest. Bill weighs three times as much as Susan. Bill pushes horizontally on Susan's back, causing Susan to start moving away from Bill. Just after Bill stops pushing, what happens to the movement and speed of both people?

Susan and Bill are moving away from each other, and Susan's speed is three times that of Bill BECAUSE Susan is lighter so her speed is greater.

An object is moving with constant non zero velocity. What must be true about the net force?

The net force on the object is zero BECAUSE it is not gaining or losing any of its speed.

Consider a deer that runs from point A to point B. The distance the deer runs can be greater than the magnitude of its displacement, but the magnitude of the displacement can never be greater than the distance it runs, true or false?

True BECAUSE keep in mind the difference between displacement and distance.

A push of magnitude P acts on a box of weight W as shown in the figure. The push is directed at an angle theta below the horizontal, and the box remains at rest. The box rests on a horizontal surface that has some friction with the box. What is the normal force on the box due to the floor equal to?

W + P cos theta.

In a position vs. time graph, which moment in time is the speed of the object the greatest?

When the slope is the greatest/steepest BECAUSE the slope of a position by time graph gives you the speed.

If the acceleration of an object is zero, then can that object be moving?

Yes BECAUSE the velocity could still be constant, it does not have to be zero for the acceleration to be zero. It just does not get faster with each time frame.

A 10 kg rock and a 20 kg rock are dropped at the same time and experience no significant air resistance. If the 10 kg rock falls with acceleration a, what is the acceleration of the 20 kg rock?

a (the same) BECAUSE gravity always remains the same!!

What does the slope of a velocity versus time graph give?

acceleration BECAUSE acceleration is how much the velocity has increased in a certain period of time.

A child standing on a bridge throws a rock straight down. If upward is taken as the positive direction, which of the graphs shown below best represent the acceleration of the stone as a function of time on an acceleration by time graph?

A horizontal line below the x axis BECAUSE acceleration does not change as time does and upwards is positive so it would be -9.8 m/s^2.

Two objects are dropped from a bridge, an interval of 1 second apart. During the time that both objects continue to fall, what happens to their separation?

It increases BECAUSE ??

A bucket is being lowered by a very light rope with a constant downward velocity. What is the tension in the rope compared to the weight of the bucket?

It is equal to the weight of the bucket BECAUSE the velocity is constant.

An elevator suspended by a vertical cable is moving downward but slowing down. What is the tension in the cable compared to the weight of the elevator?

It is greater than the weight of the elevator BECAUSE ??

If you push on box G that is next to box H, causing both boxes to slide on the floor, what is the reaction force to your push?

The push of box G against you BECAUSE normal force.

If you pound a feather with a hammer, which one feels a greater force?

The size of the force is exactly the same on both of them BECAUSE normal force is hitting the hammer back.

A stone can slide down one of four different frictionless ramps. Which ramp will the speed of the ball be the greatest, a curved one or a straight one?

The speed of the ball will be the same for all ramps BECAUSE the distance and initial velocity is the same.

James and John dive from an overhang into the lake below. James simply drops straight down from the edge. John takes a running start and jumps with an initial horizontal velocity of 25m/s. What will happen to the splashdown speed when they reach the lake below?

The splashdown speed of John is larger than that of James BECAUSE John's initial speed is greater and he his resultant vector is large because of both an x and y component.

You pull on a crate with a rope. If the crate moves, the rope's pull on the crate must have been larger than the crate's pull on the rope, but if the crate does not move, both of these pulls must have been equal, true or false?

False BECAUSE if the forces are equal and opposite, then they will move.

The collision between a huge SUV and a small hybrid car, the SUV exerts a larger force on the hybrid than the hybrid exerts on the SUV, true or false?

False BECAUSE they collide so their forces are equal and opposite; mass is not taken into account.

A truck is using a hook to tow a car whose mass is one quarter that of the truck. If the force exerted by the truck on the car is 6000 N, then what is the force exerted by the car on the truck?

6000 N BECAUSE equal and opposite.

Two frisky otters slide down frictionless hillsides of the same height but different slopes. The slope if the hill of otter one is 30 degrees, while the slope of the hill of otter 2 is 60 degrees. If both start from rest, which otter is moving is moving faster when she reaches the bottom of the hill.

Both otters have the same speed at the bottom BECAUSE they started from the same height and same initial velocity.

Mary and Debra stand on a snow covered roof. They both throw snowballs with the same initial speed, but in different directions. Mary throws her snowball downward, at 30 degrees below the horizontal; Debra throws her snowball upward, at 30 degrees above the horizontal. What is true about the speeds and time about the snowballs as they reach the ground below?

Both will hit the ground with the same speed but Mary's snowball will reach the ground before Debra's snowball BECAUSE they started with the same velocity and travel the same distance but Debra's must go up first so it will take longer.

Suppose a ball is thrown straight up and experiences no appreciable air resistance. What is its acceleration just before it reaches its highest point?

Exactly gravity BECAUSE gravity never changes.

You are in a train traveling on a horizontal track and notice that a piece of luggage starts to slide directly toward the front of the train. What can you conclude about the speed of the train?

It is slowing down BECAUSE although the train decelerates, the object at continues it's forward motion until an external force (ex. the wall in front of it) makes it stop.

A projectile is fired from ground level on a horizontal plain. If the initial speed of the projectile is now doubled, what will happen to the range?

It will quadruple BECAUSE ??

Your slam on the brakes of your car in panic, and skid a certain distance on a straight level road. If you had been traveling twice as fast, what distance would the car have skidded under the same conditions?

It would have skidded for times farther BECAUSE if the speed doubles, the stopping distance quadruples.

Two cyclists who weigh the same and have identical bicycles ride up the same mountain, both are starting at the range time. Joe rides straight up the mountain, and Bob rides up the longer road that has a lower grade. Joe gets to the top before Bob. Ignoring friction and air resistance, which of the following statements is true.

The amount of work done by Joe is equal to the amount of work done by Bob, but the average post exerted by Joe is greater than that of Bob BECAUSE they traveled the same distances and used the same force but Joe used less time.

An auto manufacturer advertises that their car can go "from zero to sixty in eight seconds". What characteristic of motion is this description?

The average acceleration BECAUSE the car increases it speed, but not at a constant rate??

A ball is thrown horizontally from the top of a tower at the same instant that a stone is dropped vertically. Which object is traveling faster when it hits the level ground below if neither of them experience any air resistance?

The ball BECAUSE it has x and y components.

Two objects, one of mass m and the other of mass 2m, are dropped from the to of a building. If there is no air resistance, when they hit the ground, what will be of their kinetic energies?

The heavier one will have twice as much kinetic energy of the lighter one BECAUSE in the equation of kinetic energy, velocity is the same but the mass is two times bigger. When solved or, the heavier I've results in twice as much kinetic energy.

What is true about an object in two dimensional projectile motion with no air resistance regarding acceleration?

The horizontal acceleration is always zero and the vertical acceleration is a non-zero constant downward BECAUSE there is no horizontal acceleration and the vertical acceleration is 9.8 and gravity always points down.

Three boxes are being pulled along a horizontal frictionless floor by a constant horizontal pull P. The boxes are connected by very light horizontal strings having tensions. What is true by the tensions of each separate string?

The tension of the string being pulled upon is greater than the last string BECAUSE it has to pull the weights of all the boxes.

In a curved graph, what value of t is the speed of the particle equal to 0 m/s?

The time of the tip of the curve BECAUSE it is a displacement by time graph and the tip has no movement, it is completely horizontal meaning there is zero velocity.

If a car and a truck drive along a straight road but the car takes diagonal path and the truck takes a straight path, when they meet, what is true about the distances each traveled?

The truck will have traveled further than the car BECAUSE the car took a cut path and creates a triangle in the graph, so if you were to solve for the displacement, you would multiply base times height but also divide by two, for the truck there would be no division so his displacement is greater??

If an object is moving in the +x direction and experiences an acceleration of 2 m/s^2, what happens to the velocity?

The velocity increases by 2 m/s every second BECAUSE if an object is accelerating, the velocity cannot remain constant and must increase as well.

What would a spring scale read if the pulleys are ideal and the strings and scales are massless when there are two weights of equal force attached on each end?

The weight of one of the weights BECAUSE it would the weight on each side cancels each other out ??

A 10 lb weight is suspended from two spring scales, each of which has negligible weight. What is true about the reading on the scales?

There is no way to know BECAUSE you do not know the magnitude of the force.

Two objects are thrown from the top of a tall building. One is thrown up, and the other is thrown down, both with the same initial speed. What are their speeds when they hit the street?

They are traveling at the same speed BECAUSE gravity accelerated them at the same rate.

A lightweight object and a very heavy object are sliding with equal speeds along a level frictionless surface. They both slide up the same hill with no friction or air resistance. Which object rides to greater height?

They both slide to exactly the same height BECAUSE ma does not matter when friction is negligible.