AP Physics 1 : AP Physics 1

Study concepts, example questions & explanations for AP Physics 1

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Example Questions

Example Question #41 : Universal Gravitation

Pluto radius: 

Pluto mass:

Determine the gravity constant,  on the surface of Pluto.

Possible Answers:

Correct answer:

Explanation:

Set both forms of gravitational force equal to each other.

Simplify:

Plug in values:

Example Question #81 : Forces

How would the linear velocity of the Moon be different if it's mass was doubled? Assume that the distance to the Earth stayed the same.

Possible Answers:

Unchanged

Quadrupled

Quartered

Doubled

Halved

Correct answer:

Unchanged

Explanation:

Set centripetal force equal to gravitational force:

The mass of the Moon, cancels out, thus, there is no effect.

Example Question #43 : Universal Gravitation

If on earth you have a weight, , what would your new weight be if you were standing on a planet with the same mass as earth, but with half the radius?

Possible Answers:

 your earth weight.

The same as your earth weight.

 times your earth weight

 your earth weight.

 times your earth weight.

Correct answer:

 times your earth weight.

Explanation:

Your weight is a function of how much force is pulling you down towards the planet, not just your mass.  To find force when your standing on a different planet, you would need to use Newton's Law of Universal Gravitation.

To compare the forces from each planet, you would set this equation equal to itself.

We then cancel the common terms, in this formula that's the negative sign,  (the gravitational constant), and the mass of the earth/planet (because they're the same).  After that we can substitute the radius of the new planet for half of the earth radius.  

We need to remember that when we square the radius in the Law of Universal Gravitation, we also need to square the , making it .  Because the  is in the denominator, we take the inverse of it, so you would feel  times more force standing on the new planet.  Therefore you would have  times as much weight.

Example Question #82 : Forces

An electronic scale is used to find the mass of a lead cube at sea level. The scale and lead cube are then transported to the top of a mountain, over  above sea level. How does the weight reading compare to the weight given at sea level?

Possible Answers:

None of these

It is impossible to determine

It will be larger

It will be the same

It will be smaller

Correct answer:

It will be smaller

Explanation:

The electronic scale measures based on the normal force the scale provides to the object. This in turn is based on the force of gravity on the object by the earth.

As height above sea level increases, as does , the distance to the center of the Earth. As  increases,  decreases. This would decrease the normal force which would decrease the reading on the scale.

Example Question #83 : Specific Forces

Mass of moon:

Radius of moon:

A spring of rest length is placed upright on the moon. A mass of is gently placed on top and the spring contracts by . Determine the spring constant.

Possible Answers:

None of these

Correct answer:

Explanation:

First, estimate the acceleration due to gravity close to the moon's surface:

Combining equations and solving for the acceleration:

Converting to and pugging in values:

Using

Solving for

Converting to and plugging in values:

(Since the mass is at rest, the acceleration and thus the net force is zero)

Example Question #53 : Universal Gravitation

A rope is used to accelerate a mass upwards at . Determine the tension in the rope.

Possible Answers:

None of these

Correct answer:

Explanation:

Using

Combining equations:

Solving for and plugging in values:

Example Question #52 : Universal Gravitation

Mass of Earth:

Universal gravitation constant: 

Radius of earth: 

Determine the magnitude of gravitational force by the earth on a   astronaut above the surface of the earth.

Possible Answers:

Correct answer:

Explanation:

Finding total distance from center of Earth to astronaut:

Converting to meters

Using Universal Gravitation equation:

Plugging in values:

Example Question #53 : Universal Gravitation

Mass of Jupiter:

Universal gravitation constant:

Radius of Jupiter: 

A marble is placed  from the surface of Jupiter. Determine the acceleration due to the gravity of Jupiter.

Possible Answers:

None of these

Correct answer:

Explanation:

Using

and

Combining equations

Solving for

Plugging in values:

Example Question #52 : Universal Gravitation

Mass of Pluto:

Radius of Pluto:

A spring of rest length  is placed upright on Pluto. A mass of  is gently placed on top and the spring contracts by . Determine the spring constant.

Possible Answers:

None of these

Correct answer:

Explanation:

First, estimate the acceleration due to gravity close to Pluto's surface:

Combining equations and solving for the acceleration:

Plugging in values:

Using

Solving for

Converting to and plugging in values:

(Since the mass is at rest, the acceleration and thus the net force is zero)

Example Question #54 : Universal Gravitation

Mass of Mars:

Radius of Mars: 

A spring of rest length  is placed upright on Mars. A mass of  is gently placed on top and the spring contracts by . Determine the spring constant.

Possible Answers:

None of these

Correct answer:

Explanation:

First, estimate the acceleration due to gravity close to the martian surface:

Combining equations and solving for the acceleration:

Plugging in values:

Using

Solving for

Converting to and plugging in values:

(Since the mass is at rest, the acceleration and thus the net force is zero)

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