Quiz #2 ANSWER KEY

A 10-kg block is pushed across a horizontal surface with a horizontal force of 20 N against a friction force of 10 N. What is the acceleration of the block in meters per second squared?

1 m/s/s a = F / m = (10 N) / (10 kg.) = (10 kg x m/s/s) / (10 kg.) = 1 m/s/s

A 1-kg rock that weighs 10 N is thrown straight upward at 20 m/s. Neglecting air resistance, what is the net force that acts on it when it is half way to the top of its path?

10 N

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

A car has a mass of 1000 kg and accelerates at 2 m/s2. What is the magnitude of the force exerted on the car?

2000 N F = ma = (1000 kg)(2 m/s/s) = 2000 N

A piece of rope is pulled by two people in a tug-of-war. Each pulls with 400 N of force. What is the tension in the rope?

400 N

A 10-N falling object encounters 4 N of air resistance. What is the magnitude of the net force on the object?

6 N

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

Your weight would increase.

Where is your gravity detector?

inner ear

A bass fiddle is louder than a harp because of what?

its sounding board

A ball is thrown vertically into the air. Because of air resistance, its speed when it returns to its starting level compared to its initial speed is what?

less than initial speed

If an electric charge is shaken up and down, what occurs?

magnetic field is created

How better are we at listening to either infrasonic sound or ultrasonic sound?

neither infrasonic sound nor ultrasonic sound

A satellite in an elliptical orbit travels at constant what?

neither velocity, acceleration, nor speed

As a ball falls, the action force is the pull of Earth's mass on the ball. What is the reaction force?

pull of ball's mass on Earth

The force exerted on the tires of a car to directly accelerate it along a road is exerted by what?

road

The natural frequency of the atoms in glass is in what part of the electromagnetic spectrum?

ultraviolet part

A blue object will appear black when illuminated with what color of light?

yellow light

A wave having a frequency of 1000 Hz vibrates at how many cycles per second?

1000 cycles per second

A floating leaf oscillates up and down two complete cycles each second as a water wave passes by. What is the wave's frequency?

2 Hz

An empty roller coaster car at an amusement park takes 3 min to make its ride from start to finish. Neglecting friction, a fully loaded car would take how long?

3 min.

A 100-kg automobile enters a freeway onramp at 20 m/s and accelerates uniformly up to 40 m/s in a time of 10 s. How far does the automobile travel during that time?

300 m (FYI...THE 100 kg WAS IRRELEVANT INFORMATION!!)

A ball is thrown horizontally from the top of a tall cliff. Three seconds later, the ball has fallen a vertical distance of what?

45 m (1 s = 5 m; 2 s = 5 m + 15 m = 20 m; 3 s = 5 m + 15 m + 25 m = 45 m)

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 what?

5 m

A 10-kg block with an initial velocity of 10 m/s slides 10 m across a horizontal surface and comes to rest. It takes the block 2 s to stop. The stopping force acting on the block is about what?

50 N

An object is placed exactly halfway between Earth and the Moon. Which of the two bodies will the object fall towards?

Earth

Relative to radio waves, the velocity of visible light waves in a vacuum is what?

In a vacuum, visible light waves have the same velocity as radio waves.

Neglecting friction, a large block of ice and a small block of ice start sliding down an incline together. When will the heavier block get to the bottom?

It gets to the bottom at the same time as the light block.

Why does an object maintains its state of motion?

It has mass.

A heavy object and a light object are dropped at the same time from rest in a vacuum. When does the heavier object reaches the ground?

It reaches the ground at same time as lighter object.

When an object falls through the air, its velocity increases. What happens to its acceleration?

Its acceleration decreases.

An object is propelled along a straight-line path in space by a force. If the mass of the object somehow becomes twice as much, what happens to its acceleration?

Its acceleration halves.

Roll a bowling ball off the edge of a table. As it falls, What happens to its horizontal component of motion as it falls?

Its horizontal component of motion remains constant.

When the distance between two stars decreases by half, what happens to the force between them?

The force between them increases to four times as much.

A speeding truck slams on its breaks and skids to a stop. If the truck were heavily loaded so it had twice the total mass, what would be its skidding distance?

The skidding distance would be the same.

Two objects move toward each other because of gravity. As the objects get closer and closer, what happens to their accelerations?

Their accelerations increase.

If your mass, the mass of Earth, and the mass of everything in the solar system were twice as much as it is now, yet everything stayed the same size, what would happen to your weight on Earth?

Your weight on Earth would quadruple.

For the astronauts inside the orbiting space shuttle, there is no force of Earth's gravity acting on them. Does this statement ever shift between being true or false?

always false

A supplier wants to make a profit by buying metal by weight at one altitude and selling it at the same price per pound at another altitude. What should the supplier do?

buy high altitude and sell low altitude

Whirl a rock at the end of a string and it follows a circular path. If the string breaks and you ignore gravity, what is the tendency of rock's movement?

follow straight-line path

According to Newton's law of universal gravitation, the greater the masses of interacting objects should result in what?

greater gravitational force between them

Two objects of the same size but unequal weights are dropped from a tall tower. Taking air resistance into consideration, which object will hit the ground first?

heavier object

Action and reaction forces comprise the parts of how many interactions.

single interaction

At a concert, a wind blows directly from the orchestra toward you. Consequently, what happens to the wavelength of the sound you hear?

sound wavelength increases