Physics Mid-term

When representing velocity as a vector,

-the direction of the arrow shows the direction of motion -the length of the arrow represents the speed -the length of the arrow is drawn to a suitable scale

A 400,000 kg airplane in takeoff uses the 40,000 N thrust of each one of its four engines. What is the acceleration of the plan during takeoff?

.4 m/s*2

A 6-N falling object encounters 6 N of air resistance. The magnitude of the net force on the object is

0

A book weighs 4 N. When held at rest in your hands, the net force on the book is

0

When an object reaches terminal velocity its acceleration is

0

When no air resistance acts on a projectile , its horizontal acceleration is what?

0

A projectile launched horizontally hits the ground in 0.8 seconds. If it had been launched with a much higher speed in the same direction, it would have hit the ground (neglected Earth's curative and air resistance) in

0.8 s

In the absence, the angle at which thrown ball will go the farthest is

45 degrees

Suppose a car is moving in a straight line and steadily increases its speed. It moves from 35 km/h to 40 km/h to 45 km/h the next second. What is the cars acceleration?

5 km/h*s

How would you show the resultant of two or more vectors?

EF=0 parallelogram rule

What is the SI unit for force?

Newtons or N

At what part of a path does a projectile have minimum speed?

at the top of its path

An airplane flying into a head wind loses ground speed, and an airplane flies at right angles to the wind, then ground speed is

more

A heavy person and a light person parachute together and wear the same size parachutes. Assuming they open their parachutes at the same time, which person reaches the ground first?

the heavy person

Pressure is defined as

force per area

Accelerations are produced by

forces

A scalar is a quantity that has

magnitude

A vector is a quantity that has

magnitude and direction

Explain how mass and inertia are related.

mass and inertia relate to each other because when one changes, the other follows. So, when an objects mass increases, the inertia increases. But, they are not the exact same. For example, if you took a stone to the moon, the mass and inertia would not change. It may be lighter, but there is the same amount of mass, and its just as hard to move.

The acceleration produced by a net force on an object is

-inversely proportional to the mass of the object -directly proportional to the magnitude of the net force -in the same direction as the net force

One possible unit of speed is

-miles per hour -kilometers per hour -light years per century

Tell the difference between scalar quantity and vector quantity.

-Scalar: magnitude -Vector: magnitude and direction

Speed is

-a measure of how fast something is moving -the distance covered per unit time -always measured in terms of a unit of distance divided by a unit of time

Aristotle's Idea of Motion

-divided motion into 2 types -violent motion-when an force acts upon it -natural motion- trying to find its natural resting point

In order to find the components of a vector, you should

-draw the vector with correct magnitude and orientation -measure the sides of the rectangle -draw a rectangle so that the vector is the diagonal

Copernicus' Astronomical Observations

-idea of heliocentric -heliocentric: means our solar system would revolve around the sun -roman church said the earth was the center of the universe (geocentric) -he had major issues with the church and didn't publish his work until right before he died

If shopping cart A has 5 times more mass in it than shopping cart B and the two carts are pushed with equal forces, you can expect the acceleration of shopping cart A to be

1/5 times that of shopping cart B

A ball is thrown straight upward at 10 m/s. Ideally the ball will return to the throwers hand with a speed of

10 m/s

A 20 kg block of cement is pulled upward (not sideways) with a force of 400 N. What is the acceleration of the block.

10 m/s*2

In the absence of air resistance, at what other angle will a thrown ball go the same distance as one thrown at an angle of 75 degrees?

15 degrees

A 20 N falling object encounters 4 N of air resistance. The magnitude of the net force on the object is

16 N

A girl pulls on a 10 kg wagon with a constant force on the object produces constant

2 m/s*2

A jet has a mass of 40,000 kg. The thrust for each of four engines is 20,000 N. What is the jets acceleration when taking off?

2 m/s*2

You push with 10 N on a 5 kg clock and there are no opposing forces. How fast will the block accelerate?

2 m/s*2

You push with 27 N on a 10 kg chest, and there is a 7 N force of friction. How fast will the chest accelerate?

2 m/s*2

A tow truck exerts a force of 2000 N on a car, accelerating it a 1 m/s/s. What is the mass of the car?

2000 kg

Suppose a small plane can fly at 170 km/h relative to the surrounding air. Suppose also that there is a 60 km/h tailwind. How fast does the plane's shadow move across the ground?

230 km/h

Suppose the force of friction on a sliding object is 25 N. The force needed to maintain a constant velocity is

25 N

When a woman stands with two feet on a scale , the scale reads 280 N. When she lifts one foot, the scale reads

280 N

A cannonball is launched from the ground at an angle of 30 degrees above the horizontal and a speed of 30 m/s. Ideally (no air resistance) the ball will land on the ground with a speed of

30 m/s

Suppose that you exert 300 N horizontally on a 50 kg crate on a factory crate on a factory floor, where friction between the crate and the floor is 100 N. What is the acceleration of the crate?

4 m/s*2

You pull horizontally on a 50 kg crate with a force of 450 N and the friction force on the crate is 250 N. The acceleration of the crate is

4 m/s*2 450-250= 200 200/50= 4

An ultra-light aircraft traveling north at 40 km/h in a 30 km/h crosswind has a groundspeed of

50 km/h

A jumbo jet cruises at a constant velocity when the total thrust of the engines on the jet is 50,000 N. How much air resistance acts on the jet?

50,000 N

A baseball is hurled into the air at an angle of 30 degrees above the horizontal and lands on a target that is at the same level as that where the baseball started. The baseball will also land on the target if it is thrown at an angle of

60 degrees

Suppose you take a trip that covers 240 km and takes 4 hours. Your average speed is

60 km/h

A cannonball is launched horizontally from a tower. If the cannon has a barrel velocity of 60 m/s where will the cannonball be 1 second later? (neglect air resistance)

60 m downrange

A sports car has a mass of 1500 kg and accelerates at 5 meters per second squared. What is the magnitude of the force acting on the sports car?

7500 N

How much force is needed to accelerate a 4.0 kg book to an acceleration of 2.0 m/s*2?

8 N

Newton's First Law of Motion:

An object at rest will stay in rest, and an object in motion will stay in motion or rest unless acted upon by a non-zero net force

T/F: The combination of all the forces that act on an object is called the net force

True

Which of the following would not be considered a projectile?

a cannonball rolling down a slope

What is needed to change an object's state of motion?

a force, which is a push or pull

Which of the following would exert the most pressure on the ground?

a women standing in high heel shoes

A vall is thrown straight up. At the top of its path its acceleration is

about 10 m/s

An object has a constant mass. A constant force on the object produces constant

acceleration

A ball thrown in the air will never go as far as physics ideally would predict because

air friction slows the ball

In the absence of air friction, the vertical component of a projectiles velocity doesn't change as the projectiles moves... (true/false?)

always false

In the absence of air friction, the horizontal component of a projectiles velocity doesn't change as the projectile moves (true/false?)

always true

Any vector can be represented by two other vectors that are

at right angles to each other

You are on a frozen pond, and the ice starts to crack, If you lie down on the ice and being to crawl, this will

decrease the pressure on the ice

When the angle of an incline with a block resting on it increases, the normal support force

decreases

The orientation of a vector shows its

direction

A ball is thrown into the air at some angle. At the very top of the balls path, its velocity is

entirely horizontal

T/F: A steel ball and a wooden ball of the same diameter are released together from the top of a tower. In the absence of air resistance they both would reach the ground at the same time. The reason for this is that the force on each ball is the same.

false

T/F: It is possible for an object in free fall to have zero acceleration

false

T/F: Perpendicular components of a vector are dependent on one another.

false

T/F: Pressure is defined as the force one object exerts on another object.

false

T/F: The pascal is a unit of force

false

T/F: The speed of an object dropped in air will continue to increase without limit.

false

T/F: When no air resistance acts on a fast-moving baseball, its acceleration is both horizontal and vertical.

false

T/F: Without air resistance, the time for a vertically tossed ball to return to where it was thrown would be less.

false

T/F: the acceleration of an object is inversely proportional to the net force acting on it

false

What is inertia?

inertia is an object's resistance to a change in motion. an example would be the resistance of trying to throw a ball into the air

When you look at the speedometer in a moving car, you can see the cars

instantaneous speed

How does acceleration of an object change in relation to its mass? It is

inversely proportional

If the force acting on a cart doubles, what happens to the carts acceleration?

it doubles

The length of a vector represents

its magnitude

A projectiles path is called

its trajectory

A rock is thrown vertically into the air. At the very top of its trajectory the net force on it is

its weight

A cannonball is fired at some angle into the air. In the first second it moves 5 meters horizontally. Assuming it doesn't hit the ground and air resistance is negligible, how far does it move horizontally in the next second?

more than 5 meters

At the instant a ball is thrown horizontally with a large force, an identical ball is dropped from the same height. Which ball hits the ground first?

neither- they both hit the ground at the same time

At the instant a ball is thrown horizontally with a large force, an identical ball is dropped from the same height. Which ball hits the ground first?

neither. they both hit the ground at the same time.

The unit of pressure is

newtons per square meter/ pascals

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

no higher

The vector sum is called the

resultant

What is friction?

the force/energy that you get from rubbing/passing of 2 objects. Friction is almost always present. You can get friction from almost anything because there will be slight discrepancies/uneven spots on objects.

A force of 3 N accelerates a mass of 3 kg at the rate of 1 m/s*2. The acceleration of a mass of 6 kg acted upon

the same

Aunt Minnie throws a rock downward, and air resistance is negligible. Compared to a rock that is dropped, the acceleration of the rock after it is thrown is

the same

A tennis ball and a solid ball with the same diameter are dropped at the same time. Which ball has the greater force acting on it?

the steel ball

When no physical changes occur within a system has reached what point?

the system with no physical changes has reached equilibrium

The upward force that balances the weight of an object is known as?

the upward force-- the support force

The horizontal component of a projectiles velocity is independent of

the vertical component of its velocity

A tennis ball and a solid ball with the same diameter are dropped at the same time. In the absence of air resistance, which val has the greater acceleration?

they would both have the same acceleration

T/F: A fluid can be either a liquid or a gas

true

T/F: The net force on an object falling at terminal velocity is zero

true

Wind Velocity can be represented as a

vector quantity

Acceleration is defined as the CHANGE in

velocity divided by the time interval

A push on a 1 kg brick accelerates the brick. Neglecting friction, to equally accelerate a 10 kg brick, one would have to push

with 10 times the force

Suppose you are in a car that is going around a curve. The speedometer reads a constant 30 miles per hour. Which of the following is NOT true?

your velocity is constant