Physics Chapter 5, 6, 7

Choose the correct statements about momentum: - Momentum is a scalar quantity. - Momentum is proportional to the mass of the object. - Change in momentum is equal to the impulse exerted on the system. - Momentum is a vector quantity. - Change in momentum is inversely proportional to the external force. - Momentum is inversely proportional to the mass of the object. - Momentum in any system is conserved. - Change in momentum is proportional to the external force. - Momentum in an isolated system is conserved.

- Momentum is proportional to the mass of the object. - Change in momentum is equal to the impulse exerted on the system. - Momentum is a vector quantity. - Change in momentum is proportional to the external force. - Momentum in an isolated system is conserved.

How would you convince somebody that the momentum of an isolated system is constant? - It is a postulate; thus, you do not need to convince anybody. - Use an example from a textbook to show that the sum of the initial and final velocities of the objects involved in a collision are the same. - Use it to make predictions about a experiment (for example, collision of two bodies), and then compare the outcome to the prediction. - Derive it from Newton's second and third laws.

- Use it to make predictions about a experiment (for example, collision of two bodies), and then compare the outcome to the prediction. - Derive it from Newton's second and third laws.

Convert Newtons to Kg

1 kg = 9.81 N

What is the gravitational acceleration?

F=ma F = G(m1m2/r²) G(m1m2/r²) = ma Gm/r²=a

What is the universal gravitational constant?

6.67×10−11 N⋅m2/kg2

A bullet fired at a door makes a hole in the door but does not open it. Your finger does not make a hole in the door but does open it. Why? - A finger exerts a smaller force but the time interval is much longer. - The bullet is too small. - The bullet goes through the door and does not exert a force at all. - The force exerted by the bullet is not enough to open the door.

A finger exerts a smaller force but the time interval is much longer.

Choose an example in which the momentum of a system is not constant. - A freely falling metal ball, with the ball and Earth as the system. - A freely falling metal ball, with the ball as the system. - A frog on a floating piece of wood jumping off the wood, with the frog and the wood as the system. - It is not possible to give an example since the momentum of a system is always constant.

A freely falling metal ball, with the ball as the system

Which force(s) from the examples described below do(es) zero work on the respective system(s)? A person pulls a sled uphill. Consider the force the person exerts on the sled. A person holds a child. Consider the force the person exerts on the child. A person uses a self-propelled lawn mower (riding mower) on a level lawn. Consider the force the person exerts on the lawn mower. A person pushes a car stuck in the snow but the car does not move. Consider the force the person exerts on the car. A rope supports a swinging chandelier. Consider the force the rope exerts on the chandelier

A person holds a child. Consider the force the person exerts on the child. A person uses a self-propelled lawn mower (riding mower) on a level lawn. Consider the force the person exerts on the lawn mower. A person pushes a car stuck in the snow but the car does not move. Consider the force the person exerts on the car. A rope supports a swinging chandelier. Consider the force the rope exerts on the chandelier

Choose which statement describes a process in which an external force does negative work on the system. The person is not part of the system. A person holds a heavy suitcase. A person slowly lowers a box from a tabletop to the floor. A person carries a bag of groceries horizontally from one location to another. A person slowly lifts a box from the floor to a tabletop.

A person slowly lowers a box from a tabletop to the floor.

What could it mean if object 1 does +10 J of work on object 2? - Object 1 exerts a 1-N force on object 2 in the direction of its 10-m displacement. - Object 1 exerts a 10-N force on object 2 in the direction of its 1-m displacement. - Object 1 exerts a 10-N force on object 2 at a 60∘ angle relative to its 2-m displacement. - All of the above - None of the above

All of the above

If the string is tied around your finger, when do you feel a stronger pull-when the rock is at the bottom of the swing or at the top? Select the correct explanation. - At the bottom. The string exerts forces of equal magnitude and opposite direction on the rock and on the finger, and the force exerted on the rock is greater at the bottom of the swing. - At the top. The string exerts the same forces on the rock and the finger at any points of the swing, and at the top of the swing the weight of the rock is also applied to the finger. - At the top. The string exerts forces of equal magnitude and opposite direction on the rock and on the finger, and the force exerted on the rock is greater at the top of the swing. - At the bottom. The string exerts the same forces on the rock and the finger at any points of the swing, and at the bottom of the swing the weight of the rock is also applied to the finger.

At the bottom. The string exerts forces of equal magnitude and opposite direction on the rock and on the finger, and the force exerted on the rock is greater at the bottom of the swing.

Newton's law of universal gravitation describes the magnitude of the attractive gravitational force Fg between two objects with masses m1 and m2 as

Fg = G(m1m2/r²)

Definition of Kinetic Energy

K = 1/2mv²

T = 2π √r³/GM This formula respresents . . .

Kepler's Third Law

Energy principle

Ki + W = Kf

Would the people on the carousel at different distances from the center have the same acceleration?

No, the acceleration is greater on the outsides of the carousel

Would the people on the carousel at different distances from the center be going the same velocity?

No, the velocity is slower in the middle than on the outside

Which of the objects below is/are accelerating? - Object slowing down while moving in a straight line - Object moving at constant speed along a straight line - Object moving at constant speed in a circle

Object slowing down while moving in a straight line and Object moving at constant speed in a circle

The period of a satellite orbiting an object of mass M at a distance r from its center is given by . . .

T = 2π √r³/GM

In which of the following is positive work done by a person on a suitcase? The person stands on a moving walkway carrying a heavy suitcase. The person holds a heavy suitcase. The person lifts a heavy suitcase. All of the above None of the above

The person lifts a heavy suitcase.

What does a period mean when discussed in circular motion?

The time for one revolution around the circle is referred to as the period and denoted by the symbol T.

A person exerts a horizontal 50 N force on a crate, causing it to move horizontally at a constant speed through a distance of 10 m. What is the work done by the person on the crate?

The work done on the crate is 500 J.

An object (the system) weighing 20 N moves horizontally toward the right a distance of 5.0 m. What is the work done on the object by the gravitational force?

The work done on the object by the gravitational force is zero joules.

Why does a satellite in a circular orbit travel at a constant speed? - The gravitational force exerted on the satellite is balanced by the centrifugal force exerted on the satellite. - There is no component of force exerted along the direction of motion of the satellite. - The sum of the forces exerted on the satellite is zero. - There is a force exerted opposite to the direction of the motion of the satellite.

There is no component of force exerted along the direction of motion of the satellite.

Let's say you have a carousel, and three people are standing at different distances from the center of the carousel. What is the period of rotation for each person standing on the carousel?

They are all the same because they all make a full rotation at the same time.

Formula for W is . . . and . . .

W = |F| |d| cosθ W = F × d

The total momentum of an isolated system is

constant

If total momentum of an isolated system is constant than that implies that momentum finally and initially are . . .

equivalent

Energy is a conserved quantity, meaning that..

if no work is done on the system, the energy of the system will not change.

equation for time

initial velocity/acceleration

A conserved quantity is constant in a(n) _______ system. For other system we can account for the changes in the conserved quantity by what is added to or subtracted from the system.

isolated

gravitational potential energy

m × g × ∆H

An example of a conserved quantity is . . .

mass

Formula for centrifugal force?

mv²/r

When 90∘<θ<180∘, cosθ is ________, and so the work done is __________.

negative; negative

But this is a common misconception. If centrifugal force were real, when you let go the string, the stone would fly _______.

off and outward

Instead of it the stone flies . . . .

off in the tangential direction

When you try to whirl a stone, you feel a force pushing you _____ . This could be the fictitious 'centrifugal force' your friend is referring to.

out

Definition of momentum

p=mv

When 0∘<θ<90∘, cosθ is _______, and so the work done is _________.

positive; positive

Constancy implies that a quantity . . . .

remain constant in time

The "artificial gravity" is created by ________the spacecraft or space station. Because of this people experience an ______ radial force exerted on them by the outer rim of the space station. This process simulates the effect of gravity.

spinning; inward

Relationship between kinetic energy and gravitational potential energy

they are equivalent, 1/2mv² = mgH

The speed v of a satellite of mass m orbiting a distance r from the center of a larger object of mass M is given by the relationship

v = √GM/r

Definition of average speed

v=2πr/T

what is the equation for radial acceleration?

v²/r

Change in Kinetic Energy is . . .

∆KE = 1/2mv² - 1/2mu²

Relationship between ∆KE and W

∆KE = W

change in gravitational potential energy

∆Ug = m × g × ∆h

impulse formula

∆p = F∆t

change in momentum

∆p = mv₁ - mv₂