High School Physics : Motion and Mechanics

Study concepts, example questions & explanations for High School Physics

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Example Questions

Example Question #36 : Understanding Distance, Velocity, And Acceleration

A bowling ball traveling with constant speed hits the pins at the end of a bowling lane  long.  The bowler hears the sound of the ball hitting the pins  after the ball is released from his hands.  What is the speed of the ball, assuming the speed of sound is ?

 

Possible Answers:

Correct answer:

Explanation:

Knowns:

 

 

 

 

Unknowns:

 

Time can be broken up as well.  There is a time that it takes the ball to roll down the lane to hit the pin.  There is also a different time for the sound to reach the person’s ear.  This adds up to the total time provided in the problem.

 



 

Equation:

 

The ball and sound both travel at constant velocities.  Therefore the equation that can best be used is

 

 

Each step must be taken into account as the ball travels down the alley and as the sound travels back.  Since the velocity of the ball is not provided, the best place to start is to find the amount of time that it takes for the sound to reach the person’s ear.

 

Rearrange the equation to solve for time.

 

 

Plug in the values for the speed of sound and the distance that the sound travels.

 

 

 

 

The total time was given.  Subtract the time that it takes the sound to travel to determine how long the ball was rolling down the lane.

 

 

 

Now, use this time in the equation with the distance of the bowling to determine the velocity of the ball

 

 

 

 

Example Question #131 : Motion And Mechanics

One of the fastest players in football ran  in . What was his average speed during this time? 

 

Possible Answers:

Correct answer:

Explanation:

Knowns:

 

 

Unknowns:

 

 

Equation: 

 

To solve this problem we need to consider the definition of speed, which is the distance traveled over a given amount of time.

 

Even though the player's speed is changing throughout the sprint (due to acceleration), we are asked to find the average speed. We can do this using the total distance and total time given. The distance is  and the time is .

 

 

 

 

 

Example Question #132 : Motion And Mechanics

During a storm, you can usually see the lightning before you hear the thunder, unless you are very close to the lightning strike. What causes this discrepancy? 

Possible Answers:

The speed of sound is much faster than the speed of light

We need to know the current of the lightning in order to determine the answer

We need to know the voltage of the lightning in order to determine the answer

The speed of light is much faster than the speed of sound

There is no definitive scientific reason for this phenomenon

Correct answer:

The speed of light is much faster than the speed of sound

Explanation:

Assuming you stand in one place, the distance between you and the lightning strike does not change. 

 

The formula for velocity is:

 

 

In this scenario, the distance travelled, , does not change. The time taken to travel this distance,  , does change. That means that the velocity must also be changing.

 

This is an indirect relationship. As  increases,  will decrease; thus, the object with a greater time of travel (sound) will have a slower velocity.

 

 

Example Question #1 : Understanding Motion With Constant Acceleration

A ball rolls to a stop after . If it had a starting velocity of , what is the deceleration on the ball due to friction?

Possible Answers:

Correct answer:

Explanation:

We are given the initial velocity, time, and final velocity (zero because the ball stops). Using these values and the appropriate motion equation, we can solve for the acceleration.

Acceleration is given by the change in velocity over time:

We can use our values to solve for the acceleration.

Example Question #1 : Understanding Motion With Constant Acceleration

An object starts moving with a velocity, . If it accelerates in such a way so that the velocity doubles every second, what will be the velocity after ?

Possible Answers:

Correct answer:

Explanation:

If the velocity doubles every second, and it starts with a velocity of , then after  it would have a velocity of:

After  it would have a velocity of:

After  it would have a velocity of:

Example Question #1 : Understanding Motion With Constant Acceleration

A ball is dropped off of a cliff with an initial velocity of . If it is in the air for  seconds, what will be its final velocity as it hits the ground?

Possible Answers:

We need to know the height of the cliff in order to solve

We need to know the mass of the ball in order to solve

Correct answer:

Explanation:

The basic formula for final velocity is:

Since the ball starts at rest, we can simplify the equation by removing the initial velocity.

Since the acceleration on the ball will be the acceleration due to gravity, , and the time will be , as per the problem, we can insert these variables into the equation to get our answer.

Example Question #3 : Understanding Motion With Constant Acceleration

A box slides along the floor. If it starts with a velocity of  , has a final velocity of , and has been sliding for , what is the average acceleration of the box?

Possible Answers:

Correct answer:

Explanation:

Acceleration is the change in velocity over the change in time.

We are given the initial and final velocities, as well as the change in time. We can use these values to calculate the acceleration.

Example Question #202 : High School Physics

A baseball leaves a pitcher's hand at  . When it crosses home plate  later, it is moving at. What is the deceleration due to air resistance?

Possible Answers:

Correct answer:

Explanation:

For this question, we will need to use the acceleration formula:

We are given the initial velocity, final velocity, and time. Using these values in the equation, we can solve for the acceleration.

Note that the acceleration is negative, showing that the ball is slowing down, or decelerating.

Example Question #4 : Understanding Motion With Constant Acceleration

What is the final velocity of a car that starts from rest and accelerates at for ?

Possible Answers:

Correct answer:

Explanation:

To solve this problem use the equation:

We are given the acceleration and time, and we can assume the initial velocity is zero since the car starts from rest. Use these values to solve for the final velocity.

Example Question #5 : Understanding Motion With Constant Acceleration

A car starts at rest and accelerates at a constant rate of . What is its velocity after ?

Possible Answers:

Correct answer:

Explanation:

Acceleration is equal to a change in velocity divided by a change in time.

.

Since the car starts at rest, the initial velocity is zero. We know the acceleration and the change in time. Using these values, we can solve for the final velocity.

We can plug in our given values and solve:

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