Physics

A stone is thrown horizontally from the top of a cliff. One second after it has left your hand its vertical distance below the cliff is

5 m

What is the force of gravity on a 500-N woman standing on Earth's surface?

500 N

A bullet is fired horizontally with an initial velocity of 300 m/s from a tower that is 20 m high. If air resistance is negligible, the horizontal distance the bullet travels before hitting the ground is

600 m

What kind of path would the planets follow if suddenly their attraction to the Sun no longer existed?

The planets would move in straight-line paths.

When you push against a wall with your fingers, they bend because they experience a force. What is this force?

The push of the wall on you bends your fingers.

How can a huge ship have an enormous momentum when it moves relatively slowly?

The ship has enormous momentum due to huge mass.

When you toss a ball upward, by how much does its upward speed decrease each second?

The speed decreases by 10 m/s each second.

Does the speedometer on a vehicle show the average speed or the instantaneous speed?

The speedometer shows instantaneous speed.

What is the source of energy that powers a hydroelectric power plant?

The sunlight that evaporated water that eventually falls as rain and fills the reservoir.

Why is the support force on an object often called the normal force?

The support force acts at a right angle to the surface. Normal is another term for "right angle."

When you weigh yourself, how does the support force of the scale acting on you compare with the gravitational force between you and Earth?

The support force is equal to the gravitational force and has the opposite direction.

Why does the unit of time appear twice in the definition of acceleration?

The unit of time appears once for the unit of velocity, and again for the time during which the velocity changes

What does ∑F∑F = 0 mean?

The vector sum of all the forces that act on an object equals zero. The forces cancel.

If you push on a heavy crate to the right and it slides, what is the direction of friction on the crate?

To the left

True or false: One watt is the unit of power equivalent to 1 joule per second.

True

How many forces are required for a single interaction?

Two forces constitute a single interaction.

What is (are) the way(s) in which the impulse exerted on something can be increased?

Two ways to increase impulse are to increase force or increase the time the force is exerted.

Why do we say that velocity is a vector and speed is not a vector?

Velocity involves both magnitude and direction. Speed involves only magnitude

Determine the resultant of two equal-magnitude vectors at right angles to each other. Assume the magnitude of each vector is V0

Vres=1.41 V0

Which depends on gravity −− weight or mass?

Weight depends on gravity

Why doesn't a heavy object accelerate more than a light object when both are freely falling?

When in free fall, the ratio of weight/mass is the same for all objects.

What is Newton's third law of motion?

Whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first object.

The amount of gravitational force that acts on the space shuttle while in orbit is

almost as much as the shuttle's weight on Earth's surface.

Inside a freely falling runaway elevator, your

apparent weight is zero.

A bullet fired from a rifle begins to fall

as soon as it leaves the barrel

A projectile is fired horizontally in a region of no air resistance. The projectile maintains its horizontal component of speed because it

is not acted on by any horizontal forces.

Minimal orbit speed about Earth is about 8 km/s. Minimal orbital speed about the Moon would be

less than 8 km/s

According to Newton, the greater the distance between masses of interacting objects, the

less the gravitational force between them.

A "weightless" astronaut in an orbiting shuttle is

like the shuttle, pulled by Earth's gravitation.

Which has a greater momentum −− a heavy truck at rest or a moving skateboard?

moving skateboard

Consider two planets in space that gravitationally attract each other. If the masses of both planets is doubled, and the distance between them is also doubled, then the force between them is

none of the above

What prevents satellites such as the space shuttle from falling?

nothing, they continually fall around earth

One kg weighs 10 NN on Earth. Would it weigh more or less on the Moon?

one kg would weigh less on the moon

Roll a bowling ball off the edge of a table. As it falls, its horizontal component of motion

remains constant

The reason the Moon does not crash into Earth is that

the Moon has a sufficient tangential speed.

Passengers in a high-flying jumbo jet feel their normal weight in flight, while passengers in the orbiting space shuttle do not. This is because passengers in the space shuttle are

without support forces

Can a machine multiply input force?

yes

Can it be said that, when two vectors are at right angles to each other, the resultant is greater than either of the vectors separately?

yes

When a vector at an angle is resolved into horizontal and vertical components, can it be said that each component has less magnitude than the original vector?

yes

A gun with a muzzle velocity of 100 m/s is fired horizontally from a tower. Neglecting air resistance, where will the bullet be 1 s later?

100 m downrange

What is the net force on a box that is being pushed to the left with a force of 49 NN while it is also being pushed to the right with a force of 62 NN ?

13N directed to the right

A ball rolls off the edge of a horizontal roof at a velocity of 10 m/s. One second later, the speed of the ball is about

14 m/s

How much tension is there in a rope that holds a 16 NN bag of apples at rest?

16N

A projectile is thrown into the air at an angle of 50° and lands on a target that is at the same level the projectile started. It will also land on the target if it is thrown at an angle of

40 degrees

What is the definition of an elastic collision?

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

What is the definition of an inelastic collision?

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

Who falls faster when wearing the same-size parachute −− a heavy person or a light person −− or do both fall at the same speed?

A heavy person

Who could lean the farthest over a cliff without falling?

A little girl wearing heavy boots.

What equation shows the relationship among velocity, time, and acceleration?

Acceleration = change in velocity/time interval

Is acceleration directly proportional to force, or is it inversely proportional to force?

Acceleration is directly proportional to force.

Do action and reaction forces act in succession or simultaneously?

Action and reaction forces act simultaneously.

What is needed to accelerate a system?

An external force

Did Aristotle believe that forces are necessary to keep moving objects moving, or did he believe that, once moving, they would move by themselves?

Aristotle believed that forces are necessary to keep objects moving.

What quantity does it change?

Energy

When is energy most evident?

Energy is most evident when it undergoes a change - as when being transferred or transformed

What is Newton's first law of motion?

Every object continues in a state of rest, or of uniform speed in a straight line, unless acted on by a nonzero force.

Which dominated Galileo's way of extending knowledge −− philosophical discussion or experiment?

Experiment

Find the examples of a vector quantity.

Force Acceleration Velocity

How does impulse differ from force?

Force is a push or pull, while impulse is the product of force and time.

What two main ideas of Aristotle did Galileo discredit?

Heavy objects fall faster than lighter objects A force is necessary to maintain motion

What test tells us whether or not a moving object is in equilibrium?

If the moving body doesn't change its velocity, it is in equilibrium. If the body changes its velocity, it is not in equilibrium.

What is the law of energy conservation?

In the absence of external work input or output, the energy of a system remains unchanged. Energy cannot be created or destroyed.

What is the name of the property of objects to maintain their states of motion?

Inertia

What does it mean to say that a quantity is conserved?

It means that the quantity remains unchanged in a process.

What quantity(ies) is(are) necessary to determine a vector quantity?

Magnitude and Direction

For which type of collision is momentum conserved?

Momentum is conserved in both elastic and inelastic collisions.

What were Aristotle's two main classifications of motion?

Natural Motion Violent Motion

Which has the greater density −− 1 kgkg of water or 10 kgkg of water?

Neither- any amount of water has the same density

What is the unit of measurement for weight?

Newton

Is it possible to design a machine that has an efficiency greater than 100%?

No because a machine that has an efficiency greater than 100% outputs more energy than it uses, therefore, the machine creates additional energy. It violates the law of energy conservation.

Can you produce a net impulse on a car by sitting inside and pushing on the dashboard?

No, because your push is internal. To change the automobile's momentum, an external force must be applied.

What quantities does air resistance depend on?

Speed Frontal area of the falling object

Find the examples of a scalar quantity.

Speed Volume Time

What equation shows the relationship among speed, distance, and time.

Speed = distance covered/travel time

Newton discovered

That gravity is universal

If the forces that act on a cannonball and the recoiling cannon from which it is fired are equal in magnitude, how does the acceleration of the cannonball compare with the acceleration of the cannon?

The acceleration of the cannonball is greater than the acceleration of the cannon due to small mass.

What is Newton's second law of motion?

The acceleration produced by a net force on an object is directly proportional to the net force, is in the same direction as the net force, and is inversely proportional to the mass of the object.

Consider a baseball that is caught and thrown at the same speed. Which case illustrates the greatest change in momentum?

The baseball being caught and then thrown back.

Consider a baseball that is caught and thrown at the same speed. Which case requires the greatest impulse?

The baseball being caught and then thrown back.

How does the direction of a friction force compare with the direction of motion of a sliding object?

The direction of friction is opposite to the direction of motion.

What is the evidence for saying whether or not work is done on an object?

The evidence is whether or not the object experiences a change in energy.

Consider hitting a baseball with a bat. If we call the force of the bat against the ball the action force, what is the reaction force?

The force of the ball against the bat.

If we push a crate at constant velocity, how does friction acting on the crate compare with our pushing force? The pushing force and the surface are horizontal.

The friction force acting on the crate is equal to the pushing force and has the opposite direction.

For the same force, which cannon imparts the greater speed to a cannonball −− a long cannon or a short one?

The long cannon

What do we call the quantity force ×× distance?

Work

In what units are work and energy measured?

Work and energy are measured in joules.

Suppose you push on a heavy crate, but not hard enough to make it slide. Does a friction force act on the crate?

Yes, opposite to your push, just enough so that ∑∑ F = 0.

Where would your weight be greater −− on Earth or on the Moon?

Your weight would be greater on Earth because of its stronger force of gravity.

If the mass of a sliding block is tripled at the same time the net force on it is tripled, how does the resulting acceleration compare with the original acceleration?

a resulting/a original=1.0

What is the acceleration of a falling object that has reached its terminal velocity?

a=0/ms^2

What is the acceleration of a 10-NN freely falling object with no air resistance?

a=9.8 m/s^2

Without air resistance, a projectile fired horizontally at 8 km/s from atop a mountain will

all of the above

If the Sun were twice as massive,

both of the above

What does "centripetal" mean?

center seeking

An object is placed exactly halfway between Earth and the Moon. The object will fall toward the

earth

What is the acceleration of an object in free fall at Earth's surface?

g =10 m/s2

If the radius of Earth somehow decreased with no change in mass, your weight would

increase

Two objects move toward each other because of gravity. As the objects get closer and closer, the force between them

increases

Where is your gravity detector?

inside your ear

A ball is thrown upward and caught when it comes back down. Neglecting air resistance, the speed with which it is caught is

the same as the speed it had when thrown upward.