MCAT Physics 1

What factors effect the magnitude of air resistance? What does each need to do to increase air resistance?

1) Cross sectional area- greater cross sectional area= more air resistance 2) Shape: less aerodynamic= more air resistance 3) Velocity: increased velocity= more air resistance

What does constant velocity or constant speed mean for 1) acceleration 2) net force 3) forces 4) direction 5) equilibrium

1) NO acceleration 2) NO net force 3) ALL forces some to ZERO 4) NO CHANGE in direction 5) THE OBJECT is in equilibrium

Explain what these formulas mean: 1) F= mgsintheta 2) Fn= mgcostheta 3) Vf= squareroot 2gh 4) a= gsintheta

1) force down an inclined plane, parallel to the surface 2) normal force on an inclined plane 3) velocity of a particle at the base of an inclined plane 4) acceleration down an inclined plane

Label the following as a vector or scalar 1) mass 2) temperature 3) velocity 4) speed 5) displacement 6) acceleration 7) force 8) work 9) energy 10) time 11) electric field/ magnetic field 12) momentum 13) impulse 14) density 15) torque

1) scalar 2) scalar 3) vector 4) scalar 5) vector 6) vector 7) vector 8) scalar 9) scalar 10) scalar 11) vector 12) vector 13) vector 14) scalar 15) vector

The difference between the actual weight and the apparent weight tells you what 2 things?

1) the buoyant force 2) the weight of that volume of fluid

List the values for density

1000 kg/m^3 1.0 g/cm^3 (1 cm ^3= 1 mL), 1 L of water= 1 kg, and 1 mL of water= 1 g

A 10kg block is submerged in water and has an apparent weight of 50N. What is the density of the block?

2 g/cm^3 50N= (5kg) x10 10kg/5kg=2kg

If a projectile has an initial vertical velocity of 30 m/s, how many seconds will it take to reach its Max height?

3 seconds

A ball is floating 3/4 submerged in a liquid with a density of a 2.0 g/cm^3. What is the specific gravity of the liquid and the density of the ball?

3/4= X/2 X= 1.5 g/cm^3 (this is 1.5 times as dense as water, so the SG of the ball is 1.5) SG of the liquid is D liquid/Dh20= (2g/cm^3)/(1g/cm^3)=2

A student hands a 4kg mass on a spring and it stretches 1m. What is the spring constant, and how far will the spring stretch if he attaches a 2kg mass.

40= k(1m) K=40 20=k(1m) K=20 Displacement is in half, so m=1/2

A 500kg elevator is being accelerated upward by a cable with a tension of 6,000N. What force does the elevator exert on the cable?

6,000N

A boat of mass X floats 1/3 submerged in a lake. If this same boat were floating in a lake on the surface of a planet with the same mass and twice the radius as Earth, what portion would be submerged? A) 1/3 B) 1/12 C) 1/6 D) 2/3

A Both the force due to gravity and the buoyant force will be affected equally, leaving the same fraction submerged

What type of force causes a changing acceleration?

A changing force.

Imagine 2 planets of masses, A and B, where A= 2B. What is the ratio of the forces between them? What is the ratio of the acceleration between them?

A is the larger planet by a factor of 2. Under Newton's third law, the ratio is still 1:1. Under the same force, the smaller planet will have twice the acceleration, therefore the ratio of acceleration is 1:2.

What is center of mass? How do you calculate Center of Mass with multiple objects?

A weighted average of mass distribution. To calculate, use : Cmass= (r1m1 + r2m2 + r3m3..) where r is the displacement vector between a reference point and each mass.

What should you think when you see projectile motion? A) Does horizontal velocity change? B) What value does horizontal acceleration equal? C) Vertical acceleration is what? D) How does vertical behavior act? E) What is time dependent on? F) Range depends on what two components of velocity? G) Time is the same for which comments of motion?

A) Horizontal velocity never changes (as long as you're ignoring air resistance) B) Horizontal acceleration always =0 C) Vertical acceleration always = 10 m/s^2 downward D) Vertical behavior is exactly symmetrical ( I.e. If ignoring air resistance, a projectile's upward trip is identical to its downward trip) E) Time in the air depends on the vertical component of velocity ONLY F) Rage depends on BOTH the vertical and horizontal components of velocity G) Time is always the same for both the X and.Y components of the motion

How will increasing the following aspects of a mass-spring system change the frequency of oscillation? A) mass on the spring B) length of the spring C) mass of the spring itself D) gravity E) the spring constant

A) increasing mass will decrease frequency B) length of the spring= no effect on frequency C) mass of spring has no effect as long as it's less massive than the object attached to it D) increasing gravity= no effect on frequency E) increasing k WILL increase frequency

How will decreasing the following aspects of a pendulum change the frequency of oscillation? A) Mass of the pendulum bob B) length of the pendulum C) gravity

A) no effect B) decrease length will increase frequency C) decrease gravity= decreasing frequency

What is Newton's third law?

Action-reaction. Whenever one object exerts a force (action) on a second object, the second object always exerts an equal and opposite force (reaction) on the first object.

What is absolute pressure?

Actual total pressure of the atmosphere, PLUS gauge reassure.

What is a field?

An invisible influence capable of exerting a force on a mass or charge

What is the apparent weight?

Apparent weight = Actual weight (aW) - Buoyant Force (F buoyant)

Any object displaces an amount of fluid exactly equal to its own volume (if fully submerged), or to the volume of whatever fraction of the object is submerged (if floating). What principle is this?

Archimedes principle

What happens to acceleration, Gravity, and air resistance at terminal velocity?

At terminal velocity, the object stops accelerating. The forces of gravity and air resistance are now balanced Mg= Fair

What is turbulence?

At velocities real fluids exhibit laminar flow. As velocity increases and especially for non-viscous fluids, flow becomes turbulent-meaning that although the net flow is still in one direction, there are random changes in direction, velocity, and so forth.

A loaded spring shoots a ball across a flat table. After the ball is no longer in contact with the spring, the acceleration of the ball will (ignore air friction): A) increase linearly B) remain constant C) Increase exponentially D) decrease linearly

B) remain constant

A water holding a tank similar to the one described above is flown in the space shuttle to a distant planet. On this planet the tank is filled to a height of 40 meters and the spigot is then opened. The velocity of the water leaving the spigot is measured and found to be 20 m/s. What is the acceleration due to gravity on this planet? A) 10.5 m/s^2 B) 5.0 m/s^2 C) 8.0 m/s^2 D) it is impossible to calculate

B) whenever using spigot, use the v=squroot (2gh) and solve for g in this case

In practice, the acceleration due to gravity is not constant 9.8 m/s^2, but varies with distance for the center of the earth. Taking this into consideration, as a falling object approaches the earth it will: A) exhibit uniform acceleration, but it's velocity will decrease B) exhibit an increasing rate of velocity change C) Exhibit a decreasing rate of velocity change D) Exhibit uniform acceleration, but it's velocity will decrease

Because g is inversely related to r, as the object approaches the earth the rate of velocity change will increases, making B true.

As the angle of incline of a plane increases, what happens to the value of a? What happens to the value of sin(theta) and cos(theta)? What happens to the normal force and to the force down the plane? What are the minimum and maximum values for acceleration down an inclined plane?

Because the acceleration down a plane is directly related to the sine of the angle, the greater the angle, the closer the sine of the angle will be to 1. Therefore, the larger the angle, the closer to acceleration will be to 9.8m/s^2. The normal force is related to cos(theta), so as the angle increases, this value gets closer to 0, therefore as the angle increases, the normal force decreases. The force down the inclined plane is also related to sin(theta), so it to will increase as the angle of incline increases. The theoretical max incline is 90 degrees, where acceleration would be 9.8m/s^2. The theoretical minimum would be a plane with no angle of incline, where acceleration down the plane would be 0.

Two planets, X and Y, are separated by a distance r and the force on planet Y due to Planet X is F. The planets move such that the force F is quadrupled. How far apart are the planets? A) 16r B) (Gmm)/r^2 C) 0.5r D) 0.25r

C

A child on a sled is traveling down a frictionless 30 degree incline. When he reaches the bottom of the hill, he is traveling 40m/s and continues across a flat piece of ground where the snow has melted. The friction caused by the ground decelerates the sled at a constant rate of 4m/s^2. How far does the sled travel before it stops? A) 30m B) 160m C) 200m D) to solve this problem, the weight of the child and sled must be known.

C 10 seconds total, and plug into x=1/2at^2

A 25kg lead ball is placed in an unknown liquid and suffers an apparent weight loss of 25N. What is the S.G. Of the unknown liquid? (Density of lead= 11.3g/cm^3) A) 5.65 B) 11.3 C) 1.13 D) 2.21

C 25N= 2.5kg 25kg/2.5kg=10 11.3/10=1.13

What is the formula for cardiac output?

CO= stroke volume X heart rate

What is located at the center of mass of the fluid displaced by the submerged object?

Center of Buoyancy

A new planet is discovered in a neighboring solar system that has twice the mass, but half the radius of Earth. How does the strength of the gravitational field on Earth (gE) compare to the strength of the gravitational field on the newly discovered planet (gN)? A) gE= gN B) gE=8gN C)2gE=gN D)8gE=gN

D

A certain block of unknown material floating on a lake has a density of 850kg/m^3. If the mass of the block is 2.5x10^4 kg, what fraction of the block is floating above the water? A) 0.50 B)0.85 C)0.35 D)0.15

D -the floating block is 0.85 more dense than water, therefore 0.15 will be floating above water

A pipe of radius r is connected to a pressurized source and has a volume flow rate of 100 m^3/s. If the radius of the pipe is tripled, and connected to the same ounce, which of the following gives the new flow rate? A) 200 m^3/s B) 33.3 m^3/s C) 300 m^3/s D) 900 m^3/s

D) Q=AV = (pi*r^2) xV= 9pi x100= 900

What does the slope on a displacement vs time graph represent? What about a velocity vs time graph?

Displacement vs time graph represents velocity Velocity vs time graph represents acceleration

Which, displacement or distance, is dependent on path? Which is independent on path?

Distance is a measurement of travel along path, curved , linear or otherwise. (How much ground an object has covered) Displacement is a vector indicating the change in position from start to end. (How far out of place an object is). Distance is dependent on path. Displacement is independent of path.

Where is center of gravity located?

Exactly at the center of mass

What is Hooke's Law?

F= kchange in X (change in X= Change in displacement of the spring from its equilibrium point, NOT the overall length of the spring)

True or False? A ball moving with twice the kinetic energy can compress a spring twice as far

False, It will transferred completely into elastic PE so we can write. KE= (1/2)kx^2. Since KE is related to the square of X, it will require 4x the KE to compress the spring twice as far.

What is Laminar Flow?

Fluid flows in pipes in concentric sheets, each with different velocities. The fastest flow is at the exact center of the pipe and the slowest is at the interface with the wall of the pipe.

What is atmospheric pressure?

Fluid pressure due to the earth's atmosphere at that location. -decreases with increased elevation

What is Newton's second law?

Fnet= ma, where Fnet is the vector sum of all force acting on the object.

Which way does the friction force vector point for a car driving east down a straight road? For a skidding car with locked brakes? For a gecko climbing a wall? For a car driving around a corner?

For the car driving east, the road and tires also points east. When a car locks its wheels, the friction points in the opposite direction of the car's tendency to slide forward. Friction would point up the wall for a gecko, because the gecko's hands would tend to slide down the wall. For a car going around the bend, momentum makes the car continue naturally in a direction tangent to the circle. Friction points toward the center of that circle, keeping it in a circular motion (ex of centripetal force)

What is fluid pressure?

Force per unit area at some point within a fluid. Therefore, atmospheric pressure is really just a type of fluid pressure wherein air is the fluid.

What is force? Give examples of force

Force= any influence capable of causing a mass to accelerate. Examples: Gravity, contact forces, electrostatic forces, torque (a force at a distance from a point of rotation), tension, magnetic forces, etc.

What is considered "no net force"

Forces are vectors and can thus sum to zero= no net force This is the same as if no force existed at all.

Anything with mass can have WHAT kind of potential energy?

Gravitational potential energy PE= -Gmm/r

What is the gravitational PE at its lowest point of a pendulum bob?

H=0

What is range?

Horizontal distance traveled; product of velocity in the X-direction and time Range= Vx * t

Two masses, Mass and Mass B, are dropped simultaneously from an airplane. Mass A is 20kg and Mass B is 10kg. Both are the same shape and size. Taking air resistance into account, Mass A: I. Will accelerate toward earth faster than Mass B. II. Will experience a greater force due to gravity than Mass B. III. And Mass B will both accelerate at the same rate. IV. Will reach a larger terminal velocity than Mass B

I, II, and IV

A skydiver carries a light plastic ball with her on a jump. After reaching terminal velocity she releases the bal and the ball flies upward relative to her position. Relative to the ground, after its release, the ball: I. Has a positive upward velocity II. Accelerates upward III. Experiences a net upward force

II & III -the ball is substantially less dense than the skydiver, has a lower terminal velocity than the skydiver. Thus, Fair>mg for the ball at the moment of release, and there will be a net upward force. This makes III true. Net upward force causes a net upward acceleration (based on F=ma)

A block on a frictionless table top experiences a constant horizontal force, F. At the moment the block reaches the edge of the table, the block and the source causing the force lose contact and the block is launched off the side of the table with an initial horizontal velocity, v. The block's I. Horizontal acceleration after leaving the table is proportional to F, according to Newton's second law. II. acceleration will remain constant from the moment it leaves the table until it strikes the ground. III. Velocity increases linearly while it is still on the table

II &III

If there is no net force, can there be acceleration? If the force increases, what happens to acceleration? If there is no acceleration, is there or could there be, a force?

If there is no net force, there can never be acceleration according to Newton's 2nd law. However, there CAN be force and no acceleration if there are other forces to counteract it. If force increases, acceleration increases. If force increases linearly, acceleration increases linearly. If force increases exponentially, acceleration increases exponentially. If there is NO acceleration, there could be a force acting on that object. However, if there is a force, we would know that it must be exactly cancels out by the sum of the other force vectors on that same object ( i.e. The object must be in equilibrium)

What is the relationship between frequency and period?

Inverse relationship between frequency and period.

If a projectile has an initial vertical velocity of 30 m/s, how long will it be in the air, how high will it go, and what will be its average velocity during the entire trip?

It will take 3 seconds to reach max height, and will take 6 seconds total. It will travel an average velocity of 15 m/s during the upward trip for 3 seconds, which means max height will by 45 m. Average velocity will be equal in magnitude to its average velocity for the upward trip, but opposite in direction, so the average velocity during the entire trip will be 0 m/s. (Since average velocity is displacement/time, and the displacement of the complete trip is 0, the average velocity is also zero).

If there's sliding, what kind of friction is it? What about no sliding?

Kinetic- sliding Static- not sliding

What is Gauge Pressure?

Measured with respect to atmospheric pressure, where atmospheric pressure is defined as zero gauge pressure. (Amount of pressure in excess of the ambient atmospheric pressure)

Can you accelerate a ball horizontally across the room by throwing it? How do you accelerate an object? -when does the ball accelerate horizontally? When does it accelerate vertically?

NO! The object must be either: 1) in contact with the object creating the force, or 2) to be under the influence of a field force (e.g. Gravitational or electrical) at that exact moment Thus, the ball only accelerates horizontally during the brief time it is in contact with the object creating the horizontal force-in this case, your hand. In the vertical direction, the ball is always accelerating (after it leaves your hand) because it is always under the influence of earth's gravitational field

Will a constant force cause an object to accelerate? What does a constant force do?

No, it will not cause the object to accelerate faster and faster. It will cause constant (non-changing) acceleration. It CAN cause an object to move faster and faster-in which case the displacement is changing non-linearly, the velocity is changing linearly, and acceleration is NOT changing at all.

What portion of the movement of a pendulum represents one cycle?

One cycle for a pendulum would be movement of the bob from one side to the other, and then back to the starting point.

In relation to a pendulum weight (or bob), when is the PE maximum or minimum? When is KE max or minimum?

PE is at a maximum at the maximum height of the bob, and is at a minimum at the bottom of the pendulum's arc. KE is at a maximum at the bottom of the pendulum's arc and is at a minimum at the maximum height of the bob.

If pressure increases at any point in a confined, incompressible fluid, it increases by that same amount at every other point within that fluid. What is this Law?

Pascal's Law. (Pressure is transmitted in all directions, undiminished, through a contained, incompressible fluid.

How does distance change as a car drives around a circular track? How does displacement change?

Race car driver on a circular path has a constantly increasing distance traveled, but a periodic displacement that is zero at regular intervals.

Friction opposes sliding or motion?

SLIDING! NOT MOTION.

Two students throw identical balls into the air with identical initial total velocities of 40 m/s. Student A throws his ball at a 50 degree angle with respect to the ground, and Student B throws his ball at a 40 degree angle. In comparison to Student A's ball, Student B's ball will remain in the air for a: A) Shorter period of time, but travels the same horizontal distance B) Longer period of time, but travels a smaller horizontal distance C) shorter period of time, but travel a greater horizontal distance

Student B will have a greater horizontal component of velocity and a smaller vertical component. A smaller vertical velocity always means less time in the air. The optimum launch angle for maximum range is 45 degrees. Because the launch angle for both balls has deviated exactly the same amount from this optimum, they will travel the same distance. So B is correct

What does a positive slope on a displacement vs time graph mean? What does a straight line on this graph mean?

Tells us that velocity is positive. The motion is to the right. Velocity is constant an therefore the object is in equilibrium

What does the location of the line above and below the X-axis tell you on the velocity vs time graph?

Tells you the sign of the velocity, regardless of whether the object is moving to the right or to the left.

What is inertia? What is mass?

The ability of an object to resist a change to its velocity A measure of an object's inertia.

What is the relationship between buoyant force and weight of the amount of fluid displaced by the object?

The buoyant force is always EXACTLY EQUAL to the weight....

Use the relationship Q= AV to explain how velocity varies as blood flows throughout the human circulatory system

The cross-sectional area of individual vessels decreases as you go from the aorta to the capillaries. However it is TOTAL cross-sectioned area that we would apply to Q=AV. Total cross-sectional area increases as you go from aorta to capillaries. Because area is greatest at the capillaries, the velocity of blood is lowest at the capillaries. The reverse is true on the return trip: cross-sectional area decreases as we go from capillaries back to the vena cava. Therefore, velocity increases.

The fluid pressure, Pgh, is larger or smaller at the object's lower surface vs upper surface? Why?

The fluid pressure will be larger at the object's lower surface due to the larger value of the h term for the deeper surface.

How do you determine objects floating in liquids?

The fraction of the object submerged= the ratio of the density of the object to the density of the liquid.

What is Newton's First Law?

The law of inertia. States that an object in motion tends to stay in motion (in same direction and at same speed) and an object at rest tends to stay at rest, unless acted upon by some net external force.

What does the sign of the slope on a velocity vs time graph tell you? Does this tell you that the particle is moving to the right or to the left?

The sign of the slope of velocity vs time graph tells us the sign of acceleration. This tells us which direction the acceleration vector points, and hence the direction of the net force. It tells us NOTHING about which way the particle is moving. Velocity and acceleration are often oriented in opposite directions.

What is an ideal, Non-Viscous flow

This is how ideal, non-viscous fluids flow. There is assumed to be no friction (drag) between the fluid and the walls of the pipe, or between fluid molecules themselves. Fluid near the wall of the pipe flows with the same velocity as fluid at the center of the pipe.

What is Poiseuille Flow?

This is how real, viscous fluids low in pipes. Real fluids exhibit laminar flow and have a leading edge that is parabolic in shape.

True or False? For any object floating in any liquid, the ratio of SG(object) to SG(liquid) will exactly equal the fraction of the object submerged in the liquid.

True

True or false? The weight of the displaced fluid is exactly equal to the buoyant force pushing up on the object.

True

True or False? A ball moving with three times the velocity can compress a spring three times as far.

True. (1/2)mv^2= (1/2)kx^2. They are directly and linearly related.

What is the difference between velocity and speed?

Velocity= rate of change of displacement Speed= rate of change of distance

What does it mean when a line is above the x-axis on a displacement vs time graph? What about below the axis?

When the line is above the x-axis, displacement is positive and the object is to the right of the origin. When the line is below the X-axis, displacement is negative and the object must be to the left of the origin.