Physics Chapter 7: Momentum

imagine that you're hovering next to the space shuttle in an Earth orbit. your buddy of equal mass, who is moving at 4 km/h with respect to the shuttle, bumps into you. If he holds onto you, how fast do you both move with respect to the ship?

(1X0) + (1X4) = 4 = (1+1)v V = 2

if the time of impact in a collisions extended by four times, how much does the force of impact change

1/4

Distinguish between mass and momentum. which is inertia and which is inertia in motion

Mass: inertia momentum: inertia in motion

What is the equation for momentum

P=mv

Jason throws a ball horizontally while standing on roller skates. He rolls backward with a momentum that matches that of the ball. Will he end up rolling backward if he goes through the motions of throwing the ball, but does not let go of it? explain in terms of Newtons third law.

all the forces are equal and opposite

when you ride a bicycle at full speed and bike stops suddenly, why do you have to push hard on the handlebars to keep from flying forward

at a sudden stop, your body would keep moving forward while the bike isn't

visualize your self on a skateboard. do you experience the greatest impulse when you catch, throw, or catch then throw a ball

catch then throwing the ball

does impulse equal momentum, or a change in momentum

change in momentum

for a constant force, suppose the duration of impact on an object is doubled.how much is the impulse increased?

doubled

for a constant force, suppose the duration of impact on an object is doubled. How much is the resulting change in momentum increased

doubles

objects collide without being permenatly deformed and without generating heat

elastic collision

distinguish between an elastic and an inelastic collision

elastic: bouncing inelastic: no bouncing

a railroad diesel engine weighs four times as much as a freight car. if the diesel engine coasts at 5km/h into a freight car that is at rest, how fast do the two coast after they couple?

equation: M1V1 + M2V2 = = (M1+ M2)V (4)(5) + (1)(0) = 20 = (4+1)V V=4

a bug and the windshield of a fast-moving car collide. Indicate whether each of the following statements is true or false. the changes in speed of the bug and of the car are the same

false

distinguish between force and impulse

force: any push or pull impulse: force X time

which has the greater mass, a heavy truck at rest or a rolling skateboard

heavy truck

distinguish between impact and impulse. which designates a force and which is force multiplied by time?

impact designates a force impulse is multiplied by time

f X t

impulse

distinguish between impulse and momentum. which is force X time and which is inertia in motion

impulse: f X t inertia: momentum in motion

a collision in which the colliding objects become distorted and generate heat during the collision

inelastic collision

in terms of impulse and momentum, why are nylon ropes, which stretch considerably under tension, favored by mountain climbers

it lengthens the time of impact

momentum of a system

law of conservation of momentum

why is it advantageous for a boxer to ride with the punch? why should he avoid moving into an oncoming punch

less effect on the force. You're adding extra mass and extra change in velocity

why do 6-ounce boxing gloves hit harder than 16-ounce gloves

less time of impact/less padding and surface area

in a car crash, why is it advantageous for an occupant to extend the time during which the collision takes place

longer impact, smaller amount of force

mass of an object multiplied by its velocity

momentum

The force that propels a rocket from the exhaust gases pushing against the rocket, the reaction to the force the rocket exerts on the exhaust gases. Explain rocket propulsion in terms of momentum conservation

momentum is both equal in opposite, in this problem

why is the Pelton Wheel an improvement over paddle wheels with flat blades

more energy because there is more force on the pelton wheel

why is more impulse delivered during a collision when bouncing occurs than during one when it doesn't

net force is greater

Jason throws a ball horizontally while standing on roller skates. He rolls backward with a momentum that matches that of the ball. Will he end up rolling backward if he goes through the motions of throwing the ball, but does not let go of it? explain.

no

if you topple from your treehouse, you'll continuously gain momentum as you fall gain momentum as you fall to the ground below. Doesn't this violate the law of conservation of momentum? Defend your answer?

no, momentum is always conserved. The ground is also coming closer to the person

which has a greater momentum, a heavy truck at rest or a rolling skateboard

rolling skateboard

suppose you roll a bowling ball into a pillow and the ball stops. Now suppose you roll it against a spring and it bounces back with an equal and opposite momentum. which object exerts a greater impulse, the pillow or the spring

spring; less time = more force

a group of playful astronauts, each with a bag full of balls, from a circle as they free fall in space. Describe what happens when they begin tossing balls simultaneously to one another

the circle will just keep getting bigger and bigger

why is it difficult for a firefighter to hold a hose that ejects large amounts of water at high speed

the force of the water is pushing the hose back while the water is getting pushed forward

in terms of momentum conservation, why does a cannon recoil when fired

the momentum from the cannon and cannonball are both equal and opposite

what does it mean to say that momentum is conserved

the momentum remains unchanged

a proton from an accelerator strikes an atom. An electron is observed flying forward in the same direction the proton was moving and at a speed much greater than the speed of the proton. What conclusion can you draw about the relative mass of a proton and an electron?

the proton's are heavier than the electron

a lunar vehicle is tested on Earth at a speed of 10 km/h. when it travels as fast on the moon, is its momentum more, less, or the same?

the same

you can't throw a raw egg against a wall without breaking the shell, but you can throw it at the same speed into a sagging sheet without breaking it. explain.

the sheet lengthens the time of impact

what difference in recoil would you expect in firing a solid ball versus firing a hollow ball from the same cannon? explain.

the solid ball will give a better recoil in the cannon

suppose you roll a bowling ball into a pillow and the ball stops. Now suppose you roll it against a spring and it bounces back with an equal and opposite momentum. if the time it takes the pillow to stop the ball is the same as the time of the contact of the ball with the spring, how do the average forces exerted on the ball compare

the spring has twice as much force

Why can Muhammad exert a greater punching force with his bare fist than he can while wearing a boxing glove

the surface area is larger when the glove is larger which means the weight and the size of the glove will be different

when the force of impact on an object is extended in time, does the impulse increase or decrease

they both increase and decrease

if a fully loaded shopping cart n empty one traveling at the same speed have a head head-on collision, which cart will experience the greater force of impact? the greater impulse? the greater change in momentum? the greater acceleration?

they're the same/same/same/the lighter one

Why do gymnastics use floor mats that are very thick

to extend the time of impact

when catching a foul ball at a baseball game, why is it important to extend your bare hands upwards so they can move downward as the ball is being caught

to lengthen the time of impact

many years ago, automobiles were manufactured to be as rigid as possible. Today's autos are designed to crumple upon impact. why?

to lengthen the time of impact to absorb the force

When jumping from a significant height, why is it advantageous to land with your knees slightly bent

to lengthen the time of impact (makes the landing longer)

a bug and the windshield of a fast-moving car collide. Indicate whether each of the following statements is true or false. the changes in momentum of the bug and of the car are the same size

true

a bug and the windshield of a fast-moving car collide. Indicate whether each of the following statements is true or false. the forces of impact on the bug and on the car are the same size

true

a bug and the windshield of a fast-moving car collide. Indicate whether each of the following statements is true or false. the impulses on the bug and on the car are the same size

true

Can Andrew produce a net impulse on an automobile by sitting inside and pushing on the dashboard? Can the internal forces within a soccer ball that will change its momentum

when he moved forward, the canoe moved backward

in terms of impulse, and momentum, why are air bags in automobiles a good idea?

when the momentum of your body shoots forward, the momentum of the air bag shoots at you. so in this case, the momentum will equal close to zero. you're also extending the time of impact

visualize your self on a skateboard. do you experience an impulse when you catch a ball and throw it again

yes

visualize your self on a skateboard. do you experience an impulse when you catch a ball of the same speed

yes

visualize your self on a skateboard. when you throw a ball, do you experience an impulse

yes

is momentum conserved for colliding objects that are moving at angles to one another? explain.

yes because momentum is always conserved

would it be a dangerous mistake for a bungee jumper to use a steel cable rather than an elastic cord

yes, the steel cord would give a big jolt and either kill or injure you

why would is be a poor idea to have the back of your hand up against the outfield wall when you catch a long fly ball

your shortening the time of impact and can potentially break your hand