ElementaryPhysics1405.summer2024
Rank PE from greatest to least at each point
A, E, C, B, D
Rank KE from greatest to least at each point.
D, B, C, E, A
Rank speed from greatest to least at each point.
D, B, C, E, A
Find the amount of energy E dissipated by friction by the time the block stops.
E = 1/2(mv^2)+mgh
What is required to change the angular momentum of a system?
External torque
A boxer rides with the punch so as to reduce ___________.
Force
How much impulse stops a 55-kg carton sliding at 4.8 m/s when it meets a rough surface? Impulse= change in momentum: Ft=Δmv
I=260 N⋅s
As the block slides down the ramp, what happens to its kinetic energy K, potential energy U, and total mechanical energy E?
K increases;U decreases;E stays the same
Calculate the kinetic energy of a 96kg scooter moving at 18 m/s Kinetic energy = 1212 mass ×× speed 22 : KE = 12mv2
KE = 1.6×10^4 J (15552 J)
In which type or kind of collision is momentum conserved: elastic or inelastic?
Momentum is conserved in elastic and inelastic collisions
For an Earth satellite in circular orbit, list all the values that do not change
Only speed, gravitational force, and distance from Earth
The quantity that is called impulse can be measured by the _______.
Product of force and time
When you whirl a can overhead by a string in a circular path, what is the direction of the force exerted on the can?
Toward the center of the circle
The center of gravity of a basketball is located _______.
at its geometrical center
When traveling twice as fast your kinetic energy is increased ___________.
by four times
What is the momentum of a 7.0-kg bowling ball rolling at 1.4 m/s? p=mv
p=9.8 kg⋅m/s
When a big fish swims into an oncoming smaller fish and swallows it, the momentum of the two-fish system _______.
remains the same
Using conversion of energy, find the speed vb of the block at the bottom at the bottom of the ramp
vb = √v^2+2gh
When two vehicles collide, momentum is conserved _______.
whether the collision is elastic or inelastic
A ball is thrown horizontally from a cliff at a speed of 10 m/s. You predict that its speed 1 s later will be slightly greater than 14 m/s . Your friend says it will be 10 m/s
you
What is the ratio of escape speed from Earth to circular orbital speed? Ignore air resistance.
1.41
Which most simplified form of the law of conservation of energy describes the motion of the block when it slides from the top of the table to the bottom of the ramp?
1/2mv^2i+mghi=1/2mv^2f+mghf
What will be the kinetic energy of a pile driver ram that starts from rest and undergoes a 10-kJ decrease in potential energy?
10 kJ
Escape speed from Earth is any speed equal to or greater than __________.
11.2 km/s
How much work is done when you push a crate horizontally with 140N across a 13-m factory floor?
1820 J 140N x 13-m
If you push a crate horizontally with 100 N across a 10-m factory floor and the friction between the crate and the floor is a steady 70 N, how much kinetic energy does the crate gain?
300 J
When the useful energy output of a simple machine is 100 J, and the total energy input is 200 J, the efficiency is _______.
50 percent
If an input of 100 J in a pulley system increases the potential energy of a load by 60 J, what is the efficiency of the system?
60%
A. From greatest to least, rank them by their vertical components of velocity.B. From greatest to least, rank them by their horizontal components of velocity.C. From greatest to least, rank them by their accelerations when they reach the top of their paths.
A. A(15ms/60º),C(10ms/50º),B(10ms/45),D(10ms/30)B. D, A, B, CC. All equal in middle
How do linear momentum and angular momentum differ?
Angular momentum depends on the distribution of mass, whereas linear momentum depends on the total mass.
Video: Projectile Motion Part A- When Dr. Hewitt releases the two projectiles, which one hits the ground first?
Both balls hit the ground at the same time
Video: Projectile Motion : Why do the two objects hit the table at the relative times that they do?
Gravity pulls the same amount on each ball, and they each drop the same distance.
At what part of an elliptical orbit does an Earth satellite have the greatest speed? The least speed?
Greatest nearest Earth; least furthest from Earth
What impulse occurs when an average force of 15 N is exerted on a cart for 3.0 s? I=Ft
I=45 N⋅s
Video: Velocity during Projectile Motion. Part B- Predict how the vertical component of the velocity will change with time after the projectile is fired.
It first decreases to zero and then increases in the opposite direction.
Is it easier for a circus performer to balance a long rod held vertically with people hanging off the other end, or the same long rod without the people at the other end, and why?
It is easier for the performer to balance a long rod held vertically with people at the other end because the rotational inertia is greater.
Is it easier to balance a long rod with a mass attached to it when the mass is closer to your hand or when the mass is farther away?
It is easier when the mass is farther from your hand
Why does the rotational inertia of the rod with the attached mass closer to your hand compare the way it does with the rotational inertial of the rod with the attached mass farther away?
Rotational inertia depends on whether the mass is farther or closer to the point of rotation. The farther the mass is, the higher the rotational inertia.
How is rotational inertia similar to inertia as studied in previous chapters?
Rotational inertia is the resistance to a change in rotational motion, which is similar to inertia which is a resistance to a change in velocity.
For an Earth satellite in an elliptical orbit, list all the values that change.
Speed, gravitational force, and distance from Earth
Video Tutor: Dropped and Thrown Balls. Part A- Which ball (if either) has the greatest speed at the moment of impact?
The ball thrown horizontally
Why doesn't the force of gravity change the speed of a satellite in circular orbit?
The force is at a right angle to the velocity.
Why is kinetic energy a constant for a satellite in a circular orbit but not for a satellite in an elliptical orbit?
The force of gravity is perpendicular to the motion in a circular orbit but not in an elliptical orbit.
How does the rotational inertia of the rod with the mass toward the bottom compare with the rotational inertia of the mass toward the top?
The rotational inertia of the rod with the mass closer to the top is greater than the rotational inertia of the rod with the mass closer to the bottom.
A rocket coasts in an elliptical orbit around Earth. To attain the greatest amount of KE for escape using a given amount of fuel, should it fire its engines to accelerate forward when it is at the apogee or at the perigee? (Hint: Let the formula Fd=ΔKE𝐹𝑑=ΔKE be your guide to thinking. Suppose the thrust F𝐹 is brief and of the same duration in either case. Then consider the distance d𝑑 the rocket would travel during this brief burst at the apogee and at the perigee.)
at the perigee
Consider again the diagrams from Part D, which are repeated here. Again, imagine that you observed the asteroid as it traveled for one week, starting from each of the positions shown. This time, rank the positions from left to right based on the distance the asteroid will travel during a one-week period when passing through each location, from longest to shortest. If you think that two (or more) of the diagrams should be ranked as equal, drag one on top of the other(s) to show this equality.
bottom, bottom right, top left, top
Consider again the diagrams from Parts D and E, which are repeated here. Again, imagine that you observed the asteroid as it traveled for one week, starting from each of the positions shown. This time, rank the positions (A-D) from left to right based on how fast the asteroid is moving at each position, from fastest to slowest. If you think that two (or more) of the diagrams should be ranked as equal, drag one on top of the other(s) to show this equality.
bottom, bottom right, top left, top
Energy cannot be_____________.
destroyed
The torque exerted by a crowbar on an object increases with increased _______.
force and leverage distance
When you lift twice the load twice as high, in half the time, the increase in potential energy is _______.
four times
Video Tutor: Ball Fired Upward from Accelerating Cart. Part A- Consider the video you just watched. Suppose we replaced the original launcher with one that fires the ball upward at twice the speed. We make no other changes. How far behind the cart will the ball land, compared to the distance in the original experiment?
four times as far
The work that is done when twice the load is lifted twice the distance is __________________.
four times as much
What force is responsible for the decrease in the mechanical energy of the block?
friction
The tangential speed on the outer edge of a rotating carousel is _______.
greater than toward the center
Cassy can get more force on the bricks she breaks with a blow of her bare hand when _______.
her hand is made to bounce from the bricks
Video: Velocity during Projectile Motion. Part A- Predict how the horizontal component of the velocity will change with time after the projectile is fired.
it stays constant
A slowly moving ship can have a greater momentum than a fast-moving racing car when _______.
its mass times velocity is greater than that of the car
Which word in the statement of this problem allows you to assume that the table is frictionless?
smooth
Fossil fuels, hydroelectric power, and wind power ultimately get their energy from _______.
the Sun
When one does twice the work in twice the time, the power expended is _______.
the same
