Chapter 8 - Physics Test
the cannon has more mass than the cannonball
A cannon recoils from firing a cannonball. The speed of the cannon's recoil is small because . . .
more mass, more momentum, and less stopping distance
A car traveling along the highway needs a certain amount of force exerted on it to stop. More stopping force may be required when the car has . . .
Inelastic Collision
A collision in which the colliding objects become distorted, generate heat, and possibly stick together.
greater
A heavy truck and a small car rolling down a hill at the same speed are forced to stop in the same amount of time. Compared to the force that stops the car, the force needed to stop the truck is . . .
twice
A moving car has momentum. If it moves twice as fast, its momentum is _____ as much.
large mass; high speed
A moving object can have a large momentum if it has a(n) _________, __________, or both.
acceleration, impulse, and momentum
A moving object on which no forces are acting will continue to move with constant . . .
doubled
A train rolls along a track with great momentum. If it rolls at the same speed but has twice as much mass, its momentum is . . .
They strike the bricks in such a way that her hand is made to bounce back, yielding as much as twice the impulse to the bricks.
Explain how a person practicing karate can break bricks with his or her bare hand.
The curved blades of the Pelton Wheel cause water to bounce and make a U-turn, producing a large impulse that turns the well.
Explain how the blades of the Pelton Wheel work?
So they can apply the greatest force possible for as long as possible.
Explain why a baseball player follows through with his or her swing.
The momentum of the cannon is equal and opposite to the momentum of the cannonball.
Explain why the total momentum of a cannon-cannonball system is zero after firing.
With force.
How can you change momentum?
The force or impulse must be exerted on the object by something outside the object, not inside, and must have a longer or shorter time interval.
How can you change the magnitude of the force as it relates to Impulse?
Greater change in velocity, hence the greater change in momentum.
If a force is increased on an object, what happens to the velocity and the momentum?
cannon-man system
If a man firmly holds a cannon when fired, then the momentum of the cannonball is equal to the recoil momentum of the _______.
no change in momentum is possible.
If no outside force is present,
exert an impulse on it.
If you wish to change the momentum of an object,
Vector
Is momentum a vector or a scalar quantity?
change in momentum
It is correct to say that impulse is equal to . . .
greater than that of the apple only if the apple bounces
Momentum is transferred to the ground when an apple falls on it. The momentum absorbed by the ground is . . .
increased time of impact
Padded dashboards in cars are safer in an accident than non-padded ones because an occupant hitting the dash has . . .
The combined momentum.
Since there is no air resistance in space, what is the only opposing force that affects two docking space stations?
the same.
Suppose you are traveling in a bus at highway speed on a nice summer day and the momentum of an unlucky bug is suddenly changed as it splatters onto the front window. Although the momentum of the bus is very large compared to the momentum of the bug, the change in momentum of the bus, compared to the change of momentum of the bug is _______.
The same.
Suppose you are traveling in a bus at highway speed on a nice summer day and the momentum of an unlucky bug is suddenly changed as it splatters onto the front window. Compared to the force that acts on the bug, how much force acts on the bus?
the same time
Suppose you are traveling in a bus at highway speed on a nice summer day and the momentum of an unlucky bug is suddenly changed as it splatters onto the front window. The time of impact is the same for both the bug and the bus. Compared to the impulse on the bug, the means the impulse on the bus is ______.
Bug
Suppose you are traveling in a bus at highway speed on a nice summer day and the momentum of an unlucky bug is suddenly changed as it splatters onto the front window. Which undergoes the greater acceleration?
True
T or F? A dropped dish is more likely to survive a fall on carpet rather than concrete, because the softness of the carpet leads to increased contact time.
True
T or F? A wrestler thrown to the floor should extend his time hitting the mat by relaxing his muscles and spreading the impulse to his foot, knee, hip, ribs, and shoulder.
True
T or F? By hitting a soft object, such as a haystack, instead of a hard object, such as a concrete wall, you extend the contact time in which the momentum is brought to zero.
True
T or F? If a system undergoes changes wherein all the forces are internal, such as an atomic nuclei undergoing nuclear decay, the net momentum of the system before and after the event is the same.
True
T or F? If the momentum of an object changes, either the mass or the velocity or both change.
False
T or F? Momentum is conserved only when interacting objects move along the same straight path.
False
T or F? Momentum is not conserved for high-speed elementary particles in bubble chambers.
False
T or F? The impulse required to bring an object to a stop and then to "throw it back again" is less than the impulse merely to bring the object to a stop.
True
T or F? The law of conservation of momentum states that, in the absence of an external force, the momentum of a system remains unchanged.
False
T or F? The momentum of the car wreck is not equal to the vector sum of the momenta of car A and car B before the collision.
True
T or F? The vector sum of the momenta is the same before and after a collision.
True
T or F? When a boxer gets punched, she should move her head away from the punch to increase the contact time and reduce the force.
True
T or F? When a firecracker bursts, the vector sum of the momenta of its fragments add up to the firecracker momentum just before bursting.
False
T or F? When jumping from an elevated position down to the ground, you should keep your legs stiff to decrease the momentum.
False
T or F? Whenever objects collide in the absence of external forces, the net momentum of both objects before the collision does not equal the net momentum of both objects are the collision.
force; time
The change in momentum depends on the ____ that acts and the length of ____ it acts.
and opposite to the force causing the cannon to recoil.
The force on the cannonball inside the cannon barrel is equal...
by something outside the object.
The force or impulse must be exerted on the object,
Momentum
The mass of a object multiplied by its velocity. p=mv
the same as
The recoil momentum of a cannon that kicks is ______ the momentum of the cannonball it fires.
twice
Two cars, one twice as heavy as the other, move down a hill at the same speed. Compared to the lighter car, the momentum of the heavier car is _____ as much.
Moving
What does an object need to be doing to have momentum?
Impulse
What is a change in momentum called?
Dropping a ball and the ball and floor are warmer.
What is an example of a perfectly elastic collision at the microscopic level?
kg*m/s
What is the unit of measurement of momentum?
Conservation of momentum and energy.
What two conservation laws are the most powerful tools in the study of mechanics?
Elastic Collision
When objects collide without being permanently deformed and without generating heat.
long time
When you are in the way of a fast moving object and can't get out of its way, you will suffer a smaller force of impact if you decrease its momentum over a . . .
Both the same
Which would produce a greater change in momentum, driving into a very massive concrete wall with no "give," or having a head-on collision at the same speed with an identical car moving toward you with the same speed?
Neither, they're the same.
You're driving down the highway and a bug hits your windshield. Which undergoes the greater change in momentum?
