Physics 1135

You are traveling in an elevator at a constant speed downward. The magnitude of your acceleration is

0

A ball tied to a string is swung with constant speed in a vertical circle as shown. Of the points shown in the figure, the tension in the string is smallest at C D B A

C (top)

A satellite of mass m is in a circular orbit R around the Earth. Determine the orbital energy of the satellite. (Hint: Kinetic + Potential)

E=-GmM/(2R)

Which of the following quantities is NOT conserved in an inelastic collision?

Kinetic energy of the system

A particle with mass M moves in a vertical circle at the end of a string of length L. The speed of the particle at its lowest point is V. At this lowest point of motion, the net force on the particle has magnitude ________ and is directed ________ .

MV^2/L , upward

Block 1 has mass M1 and is connected to block 2 of mass M2 by a massless rope that runs over a massless, frictionless pulley. The acceleration of block 1 is (a, downward). Which is true about the tension T in the rope? O M2 M1 a| \/

T > M2 g

A box of mass m is pulled with a constant acceleration a along a horizontal frictionless floor by a wire that makes an angle of θ above the horizontal. If T is the tension in this wire, then

T > ma

According to the Mathematics Peep Show cartoon, Eratosthenes suspected the Earth was round because:

The Sun and Moon are round.

A vector is a quantity that has a magnitude and a direction.

True

According to Kepler's 3rd Law, the square of a planet's orbital period is proportional to the cube of the semi-major axis length.

True

According to the Mathematics Peep Show cartoon, Eratosthenes while visiting the city of Syene (modern day Aswan) on Midsummer's Day ( the summer solstice or the beginning of the Astronomical summer) he noticed that the reflection of the Sun could be seen in the bottom of a deep well. This meant that the Sun was overhead and the rays pointed to the center of the Earth.

True

Two balls are released at different times from the same level. Ball 1 falls straight down, while Ball 2 travels along a frictionless quarter-circular track which it leaves horizontally. If air resistance is negligible, which of the following is true about their recorded kinetic energies when they hit the ground.

When Ball 2 hits the ground, it will have the same kinetic energy as Ball 1 when Ball 1 hits the ground.

You are moving along the direction of a conservative force. The potential energy due to that force is:

decreasing

As you have learned in this course, units are very important in physics. The ancient Egyptians had the unit of the stadium as a unit of length. Given that 1 Egyptian stadium is equal to 0.0979 miles, the distance from Syene to Alexandria is 5000 Egyptian stadia. It is Midsummer's Day, with no shadows in Syene , and the shadows cast in Alexandria are at an angle of 7 ∘. Determine the circumference of the Earth from the given data.

25,170 miles

The mass of a certain planet is eight times the mass of the earth. On this planet the free fall acceleration is 2g. In terms of the radius of the earth, RE, the radius of this planet is:

2Re

A girl throws a baseball of mass 0.5 kg that leaves her hand 1 meter off the ground. The highest point in its trajectory is 10 meters. How much work was done on the baseball by gravity from the the time of leaving the thrower's hand to its hitting the ground?

4.9 J

A moon of mass M and radius R is a distance D from a planet of radius 2R and unknown mass. You observe that a distance 1/3D from the moon (measured along a straight line connecting the centers of moon and planet) the net gravitational force on your spaceship is zero. The mass of the planet is

4M

Two air track carts of masses M and 4M, respectively, compress a spring. The system is released from rest. The spring drops to the ground after it has expanded. The heavy cart acquires a final speed v. What is the final speed of the lighter cart?

4V

The position of an object is given by x = at3 - bt2 + ct. The instantaneous acceleration of the object at time t is

6at-2b

A particle with total mechanical energy E is moving along the x-axis under the influence of a conservative force whose potential energy is shown in the figure. At what point does the particle have its largest kinetic energy?

A

An object has mechanical energy E and moves in the one-dimensional potential U(x) shown in the figure. Which is true?

The force points in the positive x-direction at point A.

Two identical boxes are on the same rough horizontal surface. Box 1 is pushed by a horizontal force and is moving to the right at constant speed. Box 2 is pushed by a different horizontal force and is moving to the right, speeding up. Which is true?

The friction force on box 1 is the same as the one on box 2.

A system consists of two objects that undergo a perfectly inelastic collision. The final kinetic energy of the system after the collision is zero. We can conclude:

The initial linear momentum of the system before the collision was zero.

The total force acting on an object is constant. Which can you infer?

The magnitude of the acceleration is constant.

A monkey is climbing up a fixed vertical rope with an upward acceleration of g/5. Which of the following is true?

The monkey's speed is increasing by g/5 each second

A ball is thrown straight up with some initial speed. At the highest point, which of the following is true about the ball's speed and acceleration? (Ignore air resistance.)

The speed is zero, the acceleration equals the initial acceleration.

A ball is kicked from the ground with an initial velocity V at 30° above the horizontal. At the top of its trajectory, the ball's velocity and acceleration are:

at right angles to one another

A ball of mass m hits the floor with speed v and bounces off the floor with the same speed. The angle of incidence equals the angle of rebound. The impulse delivered to the ball by the floor is

in the y-direction.

The unit of work is:

joules

A box is resting on a rough inclined surface with coefficient of static friction µ and which makes an angle θ with the horizontal. We know that the magnitude of the frictional force is given by [m] / /_θ_

mg sinθ

If a block is pulled over a rough surface at velocity v →, the work done by friction f → is:

negative

The work done by a force on an object is zero. This is the case if the force is

perpendicular to the displacement.

A book rests on a horizontal table. The reaction force to the weight force acting on the book is

the force of gravity by the book on the Earth.

A monkey is climbing up a fixed rope at constant speed. The reaction force to the monkey's weight force is

the force of gravity by the monkey on Earth.

An object moves along the x-axis from the origin to R → = 4 i ^ meters while experiencing the force F → = − 2 x i ^ (in SI units). The work done on the object by the force equals:

-16J

A soccer ball of mass M is traveling with a speed V in the positive x-direction. After being kicked by a player's foot, the ball travels in the opposite direction with a speed of 2V. What was the x-component of the impulse delivered to the ball by the foot?

-3mv I=-M(2v)-MV

An object moves along the x-axis from the origin to R → = 4 i ^ while experiencing the force F → = − 2 i ^ (in SI units). The work done on the object by the force equals:

-8 J

A rollercoaster car of mass 1000 kg travels down a quarter-circular arc of radius 20 meters. If the wheels are frictionless, how much work do the tracks do on the car as the car goes down the quarter circle arc?

0

An object is launched from a planet at escape speed. The total mechanical energy of the object at any time after launch is

0

Planet Alpha has an escape speed that is 4 times the escape speed of Planet Beta. If the diameters of the planets are the same, Alpha's mass is....

16 times Beta's mass

A car of mass M that is traveling West collides with a truck of mass 2M that is traveling North. The fused wreckage moves with speed V at an angle θ West of North as shown in the figure.

3Vsinθ

Dave pushes his son Tom across the snow on a sled. As Dave pushes, Tom speeds up. Which is true about the force Dave exerts on Tom and the force Tom exerts on Dave?

Both forces have the same magnitude.

The Mathematics Peep Show "Eratosthenes" was created in 1961 by what celebrated St. Louis architect?

Charles and Ray Eames

A spacecraft has mass m. The square of its escape speed from a planet of mass M and radius 4R is

GM/(2R)

A satellite of mass m and radius a is orbiting a planet of mass M and radius b at a distance d in a circular orbit. The satellite's kinetic energy equals

GMm/2d

You push a box against a vertical wall by applying a horizontal force P. The box is not moving. Now you decrease the push, but not enough for the box to slip. Which of the following forces decrease(s) in magnitude? | Wall | [ ]P-> |

Normal force

Force 1 has a potential energy U1(x)=ax2+bx and force 2 has a potential energy U2= ax2+bx+c, where a, b, and c are positive constants. Which of the following is true?

The force vectors are identical.

Friction force opposes motion or impending motion relative to a surface. Friction force is caused when two surfaces rub against each other. Friction force acts parallel to the surface. The types pf frictional forces are: Static Friction - which prevents motion from starting Kinetic Friction - which opposes motion in progress

True

If a net external force acts on a body, the body accelerates.

True

If an object has a line of symmetry, then the center of mass lines on it.

True

Kinetic energy is a scalar. The unit of Kinetic energy is joule.

True

A ball is dropped from a height H and collides elastically with the floor below. What is the impulse delivered to the ball by the floor?

[***]

Two cars each of mass M are both traveling at a speed v toward an intersection. The red car is traveling south and the blue car is traveling west. They collide in the middle of the intersection and the fused wreckage slides to the southwest. What is the speed of the fused wreckage?

[***]V=2v

An object moves along the x-axis. It is moving in the negative x-direction with increasing speed. The x-components of its velocity and acceleration are:

both negative

Bilbo is pushing a crate with force P, and the crate is speeding up. The force which the crate exerts on Bilbo has a magnitude that is

equal to P

A crate of mass M rests on a rough horizontal surface with coefficient of static friction µ between the surface and the crate. You are pulling on it with force magnitude P at an angle θ > 0 with respect to the horizontal. The crate does not move. You then know that the magnitude f of the frictional force satisfies

f < P

According to the Mathematics Peep Show cartoon, Eratosthenes noticed that the Sun's rays

fell in parallel lines.

A small steel ball falls vertically downward in a thick syrup. The ball is released from rest within the syrup at to = 0. For this particular ball and syrup, it is known that speed is at any time t is given by: V ( t ) = g b ( 1 − e − b t ) where b is a constant, and g has its usual meaning. Determine the magnitude of acceleration a(t) at any time t .

g e^ (− b t)

A planet has twice the mass of Earth and twice the radius of Earth. The free-fall acceleration on this planet is equal to

g/2 or 4.9/s^2

A block of mass M is released from rest at the top of a frictionless curved path. Once it reaches the bottom, it encounters a rough surface with a coefficient of friction μ between the crate and the rough surface. If the block comes to rest after sliding a horizontal distance D, height h must equal

µD