Conservation of Energy
The standard formula for the conservation of energy
The law from which the conservation of momentum derives (aka the law which we assume in order for the momentum to be conserved)
What is Newton's Third Law?
The definition of work
What is an opposing force applied over a given distance?
An object of mass m traveling at 12 m/s west collides with an object at rest, also of mass m. What can we say about the velocity of the second object after collision?
What is the velocity of the second object is 12 m/s because of conservation of momentum?
How can we tell if mechanical energy is conserved (must list 2)?
What is there is no increase in thermal energy or work being done by an external force?
The formula to calculate the increase in thermal energy if we only have a mass, a distance, and the coefficient of kinetic friction?
What is: Eth = ukFnd?
What is the impulse-momentum theorem?
What is J = Δp?
The "sign" of work (positive, negative, zero) is dependent on..... (list three angles)
What is:
Theta > 90 --> Work is negative
Theta = 90 --> Work is zero
Theta < 90 --> Work is positive
According to Newton's second law, force is a result of a change in _____ with respect to time
What is momentum? (F = ma = mv/t)
The area under a force verus time graphs tells us the....
What is the impulse?
A 4-kg box is sliding up a ramp that is h = 2.8 m high. As the box slides up the ramp, friction acts on it. The box has 150 J of kinetic energy at the bottom of a ramp and comes to a stop at the top of the ramp. How much energy is transferred to thermal energy when the box slides from the bottom of the ramp to the top of the ramp?
What is 38J?
An object is initially at rest on a horizontal, frictionless surface. Between t = 0 s and t = 5 s, a force acts on the object. The force is given by 𝐹(t) = (2 − 5𝑡)𝑖, with 𝐹 in newtons and t in seconds. What is the momentum of the object at t = 5 s? Put your answer in unit vector notation
What is (-52.5 kg*m/s)i?
A 10-kg object is at rest on a frictionless surface. It explodes into two pieces: a 3-kg piece and a 7-kg piece. Identify the true statement(s).
a. After the explosion, the magnitude of the momentum of the 7-kg piece equals the magnitude of the momentum of the 3-kg piece.
b. After the explosion, the 7-kg piece has the same speed as the 3-kg piece.
c. After the explosion, the 7-kg piece has less speed than the 3-kg piece.
d. Both (a) and (b)
e. Both (a) and (c)
What is e. Both (a) and (c)?
If you flip a pencil in the air, what kind of motion will the center of mass follow?
What is projectile motion/parabola?
During the filming of a movie, a stunt person jumps from the roof of a tall building, but no injury occurs because the person lands on a large, air-filled bag. Which one of the following best describes why no injury occurs?
a) The bag increases the amount of time the force acts on the person and reduces the change in momentum.
b) The bag increases the amount of time during which the momentum is changing and reduces the average force on the person.
c) The bag decreases the amount of time during which the momentum is changing and reduces the average force on the person.
d) The bag provides the necessary force to stop the person.
e) The bag reduces the impulse to the person.
What is b) The bag increases the amount of time during which the momentum is changing and reduces the average force on the person?
In a pickup game of dorm shuffleboard, students crazed by final exams use a broom to propel a 3-kg calculus book along a horizontal floor. The book is initially at rest. When a rightward, horizontal force P = 20 N from the broom is applied to the book, the book moves to the right with an acceleration of 1.5 m/s2 . As the book moves to the right, a frictional force of magnitude fk acts on it. What is the increase of thermal energy of the system if the book moves 3 m?
What is Eth = (15.5 N)(3 m) = 46.5 J?
A 12 kg body is moving through space (ignore gravity) in the positive direction of an x axis with a speed of 100 m/s when, due to an internal explosion, it breaks into two pieces. Piece A with a mass of 3 kg moves away from the point of the explosion with a speed of 40 m/s in the +y direction. Piece B with a mass of 9 kg has a velocity 𝑣⃗𝐵 after the explosion. Consider a system that consists of both pieces. What is the total linear momentum of this system after the explosion?
What is (1200 𝑘𝑔 ∙ 𝑚/𝑠)𝑖̂?
DOUBLE JEOPARDY (2X POINTS)
The figure shows a snapshot of block 1 as it slides along an x axis on a frictionless floor, before it undergoes an elastic collision with stationary block 2. At the time of the snapshot, the center of mass of the system is at point A (ignore points B and C). Identify the true statement(s).
a. Block 1 is more massive than block 2.
b. After the collision, block 1 is moving rightward
c. After the collision, block 1 is moving leftward.
d. Both (a) and (b)
e. Both (a) and (c)
What is d. Both (a) and (b)
Two particles collide. If the net external force on the two particle system is zero, the momentum of the two particle system will be conserved......
What is...in all collisions?
A 6-kg object is moving in a straight line with a speed of 24 m/s, and another object of mass 3 kg is at rest. No net external force acts on the two-object system. The two collide in a one-dimensional, completely inelastic collision. What is the speed of the two-object system after the collision?
What is 16 m/s?
DOUBLE JEOPARDY (2X POINTS)
Angelique, being the amazing SI that she is, begins to work on the Jeopardy at her house. She sits at the window, wondering how she can think of a question about the conservation of energy. She decides to find a 0.60 kg baseball and toss it out of the window, measuring the speed from which it is thrown, 13 m/s. She throws the baseball from a height of 5 m. Given air resistance causes an increase of thermal energy of 15 J, what would be the max height when the baseball enters the middle of its trajectory?
What is h=11 m?
A 12 kg body is moving through space (ignore gravity) in the positive direction of an x axis with a speed of 100 m/s when, due to an internal explosion, it breaks into two pieces. Piece A with a mass of 3 kg moves away from the point of the explosion with a speed of 40 m/s in the +y direction. Piece B with a mass of 9 kg has a velocity 𝑣⃗𝐵 after the explosion. Determine the x and y component of the velocity 𝑣⃗𝐵 of piece B after the explosion. Include a plus or minus sign to indicate direction
What is the x-component of 𝑣⃗𝐵 is 133 m/s and the y-component of 𝑣⃗𝐵 is -13.3 m/
A 10.0 kg object sliding on a frictionless surface has a velocity 𝑣𝑖 = 3 𝑚/𝑠 in the +x direction. The object explodes into two pieces. Piece A has a mass of 4 kg and has a velocity of 2.4 m/s in the –x direction after the explosion. Piece B has a mass of 6 kg after the explosion and a velocity 𝑣𝐵. Goal: find vB .
What is vB = 6.6 m/s?
A 60-kg man and a 50-kg woman stand at rest on frictionless ice. The man then pushes the woman. Net external force on the man-woman system is zero. Starting with Newton’s 3rd Law, explain why the momentum of the system is conserved (you must state 3 relationships).
What is: The net force on the man is equal and opposite the force on the woman (3rd Law).The net impulse on the man is equal and opposite the impulse on the woman. The change in momentum m of the man is equal and opposite the change in momentum of the woman (impulse-momentum theorem). The momentum of the system does not change.
A 60-kg man and a 50-kg woman are holding onto each other and skating due east at a speed of 4 m/s. The man then pushes the woman. After the man pushes the woman, is the momentum of the man equal and opposite the momentum of the woman? Support your answer with math and with reasoning.
What is no, their momentums are not equal and opposite because momentum is not zero (P = 440 kg*m/s)?