How can we help?

You can also find more resources in our Help Center.

Baseball

Which has more momentum, a speeding baseball or an ocean liner at rest in a harbor?

Four times

A truck moves with a certain momentum. If both its speed and its mass are doubled, how much greater is its momentum?

increase the time the momentum decreases.

If a fast-moving object strikes you, you'll experience less force of impact if you can ____________________.

The amount of impulse will be the same either way.

If your speeding car slams into a haystack and comes to rest, how will the IMPULSE that acts on it compare with slamming into a brick wall and coming to rest?

impulses is the same for both

A fast-moving massive car has a head-on collision with a slow-moving light car. Upon which is the impulse greater?

impulse.

A cannon with a long barrel fires a shell faster because the shell experiences a greater ____________________.

1000 km/h

If superman in space throws a boulder with 10 times as much mass as himself, and the boulder leaves his hands at 100 km/h, how fast does superman recoil?

0.5 m/s

Two identical gliders slide toward each other on an air track. One moves at 2 m/s and the other at 1 m/s. If they stick together, the combination slides at ____________________.

Both the same

Which requires more work, lifting a 25-kg. bag of cement 10 m. vertically, or lifting a 50-kg. bag 5 m. vertically?

25-kg. bag.

Which requires more power, lifting a 25-kg. bag of cement 10 m. vertically in 1 minute, or lifting a 50-kg. bag 5 m. vertically in 2 minutes?

twice as much

Consider two waterfalls, one twice the height of the other. The kinetic energy of each kilogram of water falling to the bottom of the taller waterfall is about ____________________.

100 J

According to the work-energy theorem, in the absence of friction, if you do 100 J of work on a cart, you'll increase its kinetic energy by ____________________.

momentum

An object that has kinetic energy must have ____________________.

9 times as much.

You have kinetic energy when you run. If you run three times as fast, you'll have a kinetic energy ____________________.

0.25 m

Consider an ideal pulley system. Pull one end of a rope downward by 1 meter with 50 N of force, and you'll lift a 200-N load a distance of ____________________.

hydrogen

Consider molecules of hydrogen gas and heavier molecules of oxygen gas that have the same kinetic energy. The molecules with more speed are ____________________.

Water

Which will roll faster down an inclined plane, a can of water or a can of ice?

light end, where the handle is

A baseball bat has a greater rotational inertia about an axis at its ____________________.

center of mass

Toss a baseball bat through the air and it wobbles about its ____________________.

torque equals 0

A condition for mechanical equilibrium is that the sum of the forces acting equal zero. Another condition is that the sum of the ____________________.

beveled shape of the wheel circumference.

The main reason railroad trains remain on their tracks has to do with the ____________________.

For work, distance and force are in the same direction; for torque they are perpendicular to each other.

When we studied the concept of work, we learned that work = force x distance. Now we learn that torque = force x distance. What's different about these two definitions?

angular speed.

When a skater brings her arms in when spinning, she increases her ____________________.

Faster

Very ideally, and very strictly speaking, the falling leaves in autumn make the world spin a bit

Because you're not twice as far from the Earth's center.

Why is your weight not one-quarter as much when you climb to the top of a twice as tall tree?

Doctor

Which gravitationally pulls more on a newborn baby, Planet Mars or the doctor delivering the baby?

one quarter

If the radius of the Earth somehow bloated to twice its size, with no changes in mass, your weight at the Earth's new surface would be ____________________.

earth

Which of these three produces a greater tidal effect on you right now—the moon, the Earth, or the sun?

False

The gravitational field of the Earth is very weak up there in space-shuttle territory, compared to down here on the Earth's surface. True or False?

horizontal component

When you roll a ball off the edge of a table, the component of velocity that doesn't change as it falls is the ____________________.

14 m/s

Atop a cliff, a projectile is fired horizontally with an initial speed of 10 m/s. Neglecting air drag, what is its speed 1 second after it is fired?

no higher

Jose can jump vertically 1 meter from his skateboard when it is at rest. When the skateboard is moving horizontally, Jose can jump ____________________.

atmosphere

The reason a satellite such as the space shuttle remains in orbit is because it is above the Earth's ____________________.

Nothing! Its in free fall!

What force prevents a satellite or the Moon from falling toward the Earth??

an elliptical orbit

The force of gravity does work on a satellite when it is in ____________________.

Yes both would increase

If Jupiter were pulled into a tighter orbit by the sun, would both its angular speed and its linear speed increase?

accelerations

Whenever an interaction occurs in a system, forces occur in equal and opposite pairs. Which of the following do not always occur in equal and opposite pairs?

less

Strictly speaking, when a gun is fired, compared with the momentum of the recoiling gun, the opposite momentum of the bullet is

to the right, forward

An ice sailcraft is stalled on a frozen lake on a windless day. A large fan blows air into the sail. If the wind produced by the fan strikes and bounces backward from the sail, the sailcraft will move

the same

The brakes are slammed on a speeding truck and it skids to a stop. If the truck were heavily loaded so it had twice the total mass, the skidding distance would be

the middle

On a roller coaster, In which car will you be moving the fastest at the very bottom of the incline?

come to the top

When a person shakes the basketful of berries, the larger berries will

Regular

Which will roll down a hill faster, a can of regular fruit juice or a can of frozen fruit juice?

the shaken can loses!

Roll a pair of identical cans of carbonated beverage down an incline. You won't be surprised to find they roll at the same rate. Now shake one of them so bubbles form inside, then repeat the experiment. You'll be delighted to observe that

bare stick

A pair of upright metersticks, with their lower ends against a wall, are allowed to fall to the floor. One is bare, and the other has a heavy weight attached to its upper end. The stick to hit the floor first is the

remains unchanged

When a tether ball wraps around a pole, the speed of the ball

nearly as much

When at rest on the launching pad, the force of gravity on the space shuttle is quite huge—the weight of the shuttle. When in orbit, some 200 km above Earth's surface, the force of gravity on the shuttle

oscillate to and fro.

Consider a giant flat plate that touches the Earth at one point and extends out into space. Suppose you slide an iron block along the plane, where it makes contact with the Earth.Suppose also that the plate is perfectly frictionless, air drag is absent, and vo < vescape. The block will

continue in its normal orbit

If the Sun suddenly collapsed to become a black hole, the Earth would

Yes, but negligible

Ocean tides are produced by the Moon. Since our bodies aremostly water, doesn't the Moon similarly produce tides in our bodies?

momentum

the product of a body's mass and its velocity

impulse

the product of the force acting on an object and the time during which it acts. A change in momentum.

Law of conversion of momentum

In the absense of an external force,the momentum of a system remains unchanged.

elastic collision

A collision in which colliding objects rebound without lasting deformation or the generation of heat.

inelastic collision

A collision in which the colliding objects become distorted, generate heat, and possibly stick together.

Work

w=fd

Power

work done/ time interval

energy

the properties of a system that enables it to do work

potential energy

the energy that an object has because of the position, shape, or condition of the object

kinetic energy

the energy of motion

tangential speed

linear speed along a curved path

rotational speed

Number of rotations or revolutions per unit of time

rotational inertia

property of an object that measures its resistance to any change in its state of rotation

torque

lever arm * force

center of mass

the average position of the mass of an object.

center of gravity

the average position of an object's weight where gravity acts

centripetal force

the force towards a fixed point, usually in circular motion

centrifugal force

apparent outward force on a rotating or revolving body

angular momentum

The product of a body's rotational inertia and rotational velocity about a particular axis.

conservation of angular momentum

When no external torque acts on an object or a system of objects, no change of angular momentum can occur. Hence, the angular momentum before an event involving only internal torques or no torques is equal to the angular momentum after the event.

law of universal gravitation

All objects in the universe attract each other through gravitational force.

inverse-square law

a law relating the intensity of an effect to the inverse square of the distance from the cause

spring tides

Tides that occur when the sun, earth, and moon are aligned

neap tides

a tide that occurs when the moon is halfway between a new moon and a full moon, in either direction; the tides due to the sun and the moon partly cancel, so that the high tides are lower than average, and the low tides are not as low s average

gravitational field

The influence that a massive body exends into the space around itself, producing a force on another massive body

projectile

Any object that moves through the air or through space under the influence of gravity.

parabola

the curved path followed by a projectile under the influence of constant gravity only

satellite

An object that revolves around another object in space

ellipse

A elongated circle, or oval shape, the shape of the planets or satellites in orbit.

Kepler's laws

Kepler's first law states that the planets travel in elliptical orbits with the sun at one focus. When planet is farthest from sun it is at its aphelion, closest at it's perihelion. Second Law states equal area law and says each planet moves around the sun in such a way that an imaginary line joining the planet to the sun will sweep over equal areas of space in equal time periods. The third law is the harmonic law that says the period of a planet squared is equal to the cube of it's distance from the sun. The farther it is from the sun, the longer it's period of revolution.