Physic 1 homeworks

A car is moving on a highway with a speed of 10 m/s. 5 seconds later the car is moving at 40 m/s in the same direction. The car's acceleration is

+6m/s^2

A car is moving on a highway at a speed of 20 m/s to the north direction. Two seconds later the car is moving at 70 m/s in the opposite direction (south direction). Let's consider towards the north is our + direction. The car's acceleration is

-45 ms-2

A car is moving on a highway with a speed of 40 m/s. 5 seconds later the car is moving at 10 m/s in the same direction. The car's acceleration is

-6 m/s2

If you throw a baseball straight up, what is its velocity at the highest point it reaches?

0

for an object that thrown straight up, in the presence of air or in a vacuum, what is the velocity of the highest point of its trajectory?

0

What is the velocity of the object at the top of its path

0 m/s

According to Newton's gravitational law, the acceleration is given as Where G is the gravitational Constance: 6.674×10−11 m3⋅kg−1s−2 Mass of earth = 5.972 × 1024 kg, In Mars closest approach to earth, the distance from Earth to Mars = 54.6 million kilometers = 5.46 x 1010 m. What is the gravitational acceleration on Mars due to the earth at its closest approach to Earth?

1.34 x 10^-7 m/s^2

A car goes from 0 m/s to 10 m/s in 1 second, moving along the positive x-axis. What is its acceleration?

10 m/s2

A car is moving on a highway at a speed of 20 m/s. 5 seconds later the car is moving at 70 m/s in the same direction. The car's acceleration is

10 m/s2

What is the acceleration of the object at the top of its path

10 m/s2 downward

For an object that thrown straight up, in a vacuum, what is the acceleration of the highest point of its trajectory?

10 m/s^2 downward

What is the acceleration of a ball that is dropped off the side of a cliff after 1,2,3,4,5 seconds? (assume g is rounded to 10 m/s2)

10,10,10,10,10 m/s2

An object is in a free fall under the earth's gravitational acceleration, how far does it fall in 5 seconds? ( use the equation for distance when acceleration is present, d = 1/2 g t2)

125 meters

Ann travels 10 miles east and then goes 3 miles west. What is her distance travel?

13 miles

A ball is thrown up in the air with an initial velocity of 40 m/s. What is the ball's velocity after 2 seconds?

20 m/s traveling upward

In the physics world, (no air) Suppose that an object is thrown upwards at a speed of 30 m/s. How long will it take to reach the highest point of the trajectory?

3 seconds

A ball is thrown upward in the air with an initial velocity of 40 m/s. How long does it take to reach the top point of its motion?

4 seconds

A car starts from rest and reaches 20 m/s in 5 seconds. The average acceleration of the car is

4.0 m/s^2 Yes, Initial velocity is zero, so final velocity - initial velocity is 20 m/s And the time interval is 5 s so acceleration is 4m/s^2

What is the distance a ball falls after 1,2,3,4,5 seconds (assume g is rounded to 10 m/s2)?

5, 20, 45, 80,125 m (meters)

An object free falls for 3.5 seconds. How far does it fall? Use the equation d = 0.5(gravity)t2

61.25

Ann travels 10 miles east and then goes 3 miles west. What is her displacement?

7 miles east

A ball is thrown upward in a vacuum with an initial velocity of 40 m/s. How long does it take to reach back to the point it was thrown from? (consider gravitational acceleration is 10 m/s2)

8 seconds Every second the object slows down by 10 m/s and on the way back it gains speed by 10 m/s at every second.

What is a scientific theory?

A scientific theory is an explanation of natural phenomena that is supported by evidence.

Drop two objects at the same time, both fairly heavy so that air resistance can be neglected. Aristotle would say that the heavier object should reach the ground long before the lighter one. Do you agree?

Actually they hit the ground at the sametime, as the air friction can be negligible.

What is the difference between an observation and a hypothesis?

An observation is seeing what happens; a hypothesis is a testable, educated guess.

The diagram shows the positions at 0.05-sec intervals of two balls moving left to right. Are either or both balls accelerated?

Both balls are accelerated

Which would hit the ground first if dropped from the same height in a vacuum—a feather or a metal ball?

Both would hit the ground at the same time.

What is the difference between distance and displacement?

Displacement is a vector and distance is a scalar

Without air resistance, a projectile fired horizontally at 25,000 mph from atop of a mountain would

Escape from the Earth

Who throws balls from the leaning Tower of Pisa?

Galileo Galilei

Without air resistance, a projectile fired horizontally at 17,000 mph (8 km/s) from atop of a mountain would

Go into a circular orbit around the Earth.

we continue to neglect the influence of air resistance, In projectile motion the vertical acceleration of the trajectory is

Gravity (10 m/s2) downward

Which of the following statements is an observation of the natural world?

I saw the Moon rise at 6:52pm yesterday

What does this motion graph represent?

I walked home from school at a constant velocity, played Fortnite for a while, then studied then ran back to the school

Which quantity is the highway patrol more interested in?

Instantaneous speed

When an object falls in physics world (no air), what happens?

It accelerates at a constant rate until it hits the ground

In one dimensional motion, the average velocity of an object that moves from one place to another and then back to the original place has which of the following properties?

It can be positive, negative or zero

Which statement best compares and contrasts the aims and topics of natural philosophy had versus physics?

Natural philosophy included all aspects of nature including physics.

For an object that thrown straight up, in a real-world in the presence of air, what is the acceleration of the highest point of its trajectory?

Non zero and should be donward

A negative distance implies that an object is

On the negative side of the origin

Sarah reports that she saw a green star close to the star Betelguese. Actually, she did not even look there. The most likely outcome of her fraud is that:

Other people look near Betelgeuse. They do not see the green star, and attack her report as a mistake or a fraud.

How do physical therapists use physics while on the job?

Physical therapists require knowledge of physics to know about muscle contraction and release of energy.

What subfield of physics could describe small objects traveling at high speeds or experiencing a strong gravitational field?

Quantum relativity

The movie "theory if everything" is about

Stephen Hawking

In a vacuum, An object is shot directly upward from the ground. T1 represents the time it takes to reach the maximum height. T2 represents the time it takes to travel from the maximum height to the ground.

T1 = T2

What is meant when a physical law is said to be universal?

The law applies everywhere in the universe.

Statements that belong in science must be about reproducible observations. However, as Karl Popper pointed out, there is a much stricter requirement. A scientific statement is one that could possibly be proven wrong. Such a statement is said to be falsifiable Which of the following statements is falsifiable?.

The moon is made entirely of cheese

Which would fall with greater acceleration in a vacuum—a leaf or a stone?

They would accelerate at the same rate. (remember the mothere earth)

No air friction, Which of these three balls would hit the floor first if all three left the tabletop at the same time?

They would all hit at the same time.

Three small marbles with the same weight left the tabletop at the same time at different horizontal velocities. V1 < V2 < V3. Which of these three balls would hit the floor first?

They would all hit at the same time.

You throw a football horizontally and drop a football from the same height and at the same time. Which will hit the ground first? Remember: we continue to neglect the influence of air resistance

They would all hit at the same time.

Projectile motion is a

Two Dimentional Motion

we continue to neglect the influence of air resistance, In projectile motion the horizontal acceleration of the trajectory is

Zero

Which graph shows an object standing still?

a

Which of the following would NOT be considered a projectile?

a cannon ball rolling down a slope

An object undergoing free-fall in a vacuum experiences

a constant acceleration.

Speed is

a scalar quantity

Velocity is

a vector quantity

Which of the two trajectories shown will result in a long time for the ball to reach home plate?

a)The higher trajectory takes longer. The time of flight is determined by the initial vertical velocity component which also determines the maximum height reached.

Which free-throw trajectory has the greatest chance of success?

a)The upper path is more likely to go thru if the ball player has the same control for either path.

The slope of the velocity versus time graph is the

acceleration

Which graph shows an object moved with a constant velocity?

b

A stone is dropped from a cliff at time t=0 and strikes the ground below. Which of the following graphs best shows the velocity vs time of the stone after it is dropped? Assume upward is the positive direction.

c

Which graph shows an object been accelerated?

c

Acceleration represents the

change in velocity with respect to time

This following graph represents:

constant velocity

This is a velocity-time graph. What is the object motion between B to C ?

constant velocity

Projectile motion is characterized by

constant velocity in the x direction and constant acceleration in the y direction towards the ground

Projectile motion is characterized by

constant velocity in the x-direction and constant acceleration in the y direction

A stone is thrown upward from a cliff at time t=0. In return, the stone passes the cliff and strikes the ground below. Which of the following graphs best shows the velocity vs time of the stone after it is thrown?

d

Average speed is calculated by

dividing the distance traveled by the elapsed time

Average speed is calculated by?

dividing the distance traveled by the elapsed time

The value for the acceleration due to gravity is ms-2

downward 9.8 ~ 10

The graph represents the distance variation overtime for two runners coded in green and blue color. Which runner has a greter speed?

green

A freely falling object (neglecting air resistance) has its velocity

increasing linearly with Time

After it passes the peak of the path of its motion an object thrown upward has

its velocity directed downward and its acceleration directed downward

Just before it reaches the peak of the path of its motion, an object thrown upward has

its velocity directed upward and its acceleration directed downward

When a large body of experimental evidence supports a hypothesis, what may the hypothesis eventually be considered?

law

In the real world (with air) Suppose that an object is thrown upwards at a speed of 30 m/s. How long will it take to reach the highest point of the trajectory?

less than 3 seconds, if we know the weight then we can do the calculation

The basic unit of length in the metric system is the

meters

This is a velocity-time graph. What is the object motion between C to D ?

negative acceleration

In projectile motion in real life with air around the motion, the horizontal component of the velocity at the top of the trajectory is

non-zero, and greater than or less than the initial horizontal component of the velocity depending on the wind velocity.

In projectile motion the velocity at the top of the trajectory is

non-zero, since the horizontal (x) component of the velocity has remained constant.

This is a velocity-time graph. What is the object motion between A to B ?

positive acceleration

A spherical shape metal ball with a small diameter dropped from rest from a tall building when we do the calculations

the air resistance can be neglected.

A ball is thrown upwards and caught when it comes back down. In the absence of air resistance, the speed of the ball when caught would be

the same as the speed it had when thrown upwards.

In the case of uniform accelerated motion, the graph of velocity versus time is a straight line angled to the time axis.

true

The slope of the distance traveled versus time graph is the

velocity

A car goes around a curve at a constant speed. Is the car's velocity changing?

yes

In projectile motion the vertical velocity at the top of the trajectory is

zero

In projectile motion with the presence of air the vertical component of the velocity at the top of the trajectory is

zero, otherwise the object can not fall back.