AP Physics 1 : Newton's Second Law

Example Questions

Example Question #49 : Fundamentals Of Force And Newton's Laws

baseball player slides, making contact with the ground causing a force of kinetic friction measured at . What is the acceleration that acts on this superstar due to friction during the slide?

Explanation:

Firstly, put the given values into the proper units.

Now use Newton's second law to determine the acceleration.

He will decelerate at .

Example Question #50 : Fundamentals Of Force And Newton's Laws

Kaden lives on the 4th floor at an apartment complex. Instead of making multiple trips up and down the stairs he elects to use a rope and bucket system to get his groceries up to his balcony. If Kaden applies  of tension on the rope tied to the bucket. What mass (in kilograms) of groceries can he carry in each load? Assume that both the bucket and rope are weightless and neglect friction.

Explanation:

The bucket is not accelerating in either direction so the tension force must be equal to the weight of the groceries.

Multiplying mass and gravity gives weight

Plug in and solve for the mass

Kaden can carry a maximum of  of groceries in each load up to his balcony.

Example Question #51 : Fundamentals Of Force And Newton's Laws

A pitcher throws a fastball at  and the catcher brings the ball to a complete rest over a distance of . What force did the catcher exert on the baseball to bring it to rest? .

Explanation:

First, convert to metric units.

Now, use the equation for velocity.

Plug in and solve for the final time.

Now use the equation for acceleration.

Plug in and solve for the acceleration.

Use Newton's second law to solve for the force.

Plug in and solve for the force that the catcher exerts on the ball.

The catcher will exert an amazing  of force to stop the fastball in such a short distance.

Example Question #52 : Fundamentals Of Force And Newton's Laws

Cody pulls his  brother on the fresh snow during Christmas break. In order for his brother to have fun he must pull him at a constant speed of . The coefficient of kinetic friction between the sled bottom and the fresh powder is . What horizontal pulling force must Cody apply to give his brother a fun ride? Assume the sled has no mass and neglect air resistance.

Explanation:

The weight is being compensated by the normal force.

Weight is equal to mass times the acceleration due to gravity.

The sled does not have to accelerate so the kinetic frictional force is equal to the pulling force .

The equation for kinetic frictional force is inserted below.

Plug in and solve for the pulling force.

Cody must apply at least  of horizontal pulling force.

Example Question #53 : Fundamentals Of Force And Newton's Laws

In the military a paratrooper and his/her gear can weigh in excess of . While skydiving, a paratrooper can experience an upward acceleration of  when he/she opens the parachute. What force does the paratrooper experience at this time?

Explanation:

The weight of the paratrooper and his or her gear is

Plug in and solve for the mass.

The force due to air resistance causes an acceleration of .

Plug in and solve for the force due to air resistance.

The paratrooper is accelerating upward so we know that the force due to air resistance is greater than the force of gravity.

Plug in the known values and solve for the combined net force.

Example Question #54 : Fundamentals Of Force And Newton's Laws

A new start up shoe company claims to make the lightest basketball shoe that still produces tremendous grip to allow players to move smoothly and freely throughout the game. In a laboratory test done on typical hard wood floor revealed that the  shoe when swung at  takes  to come to a complete stop. Neglecting air resistance, what is the coefficient of kinetic friction between the shoe bottoms and the hard wood floor?

Explanation:

Use the equation for velocity.

Plug in and solve for the final time.

Now use the equation for acceleration.

Plug in and solve for the acceleration.

Now use Newton's second law.

Plug in and solve for the kinetic frictional force.

Now solve for the normal force.

Plug in and solve for the normal force.

Now solve for the coefficient of kinetic friction.

Plug in and solve for the coefficient.

The coefficient of kinetic friction between the floor and the bottom of these shoes was determined to be

Example Question #31 : Newton's Second Law

John has just finished chopping a bunch of firewood and has to get it in a pile by his house. He elects to use a sled to pull the wood across the gravel road to his house. The road and the sled maintain a coefficient of static friction determined to be . John is able to cram  of wood into the sled. After chopping all the wood he is tired but convinced he can move the sled. If John can pull with a max force of  can he pull the sled to his house and if not how many newtons of force is he short?

No, he would need  more.

No, he would need  more.

No, he would need  more.

Yes, the  will suffice to move the sled up to his house.

No, he would need  more.

Explanation:

The sled and wood has a mass of

Plug ina and solve.

Use the equation for static friction.

Plug in and solve for the static frictional force.

John will not be able to move the sled and would have to double his efforts to move it.

Example Question #56 : Fundamentals Of Force And Newton's Laws

During time period , a rocket ship deep in space of mass travels from to . During time period , the rocket fires. During time period , the rocket travels from  to .

Time periods , and all took

Determine the average force during time period .

None of these

Explanation:

Finding initial momentum:

Combining equations:

Plugging in values:

Combining equations:

Converting to and plugging in values:

Using

Plugging in values:

Using:

Solving for and plugging in values

Example Question #31 : Newton's Second Law

Which of the following scenarios is an example of no net force being involved?

A mass attached to a pendulum moves back and forth with constant frequency

A box is lowered at a constant speed

An apple falls from a tree

A person on a ferris wheel moves at a constant speed

A car gradually slows down as it approaches a red light

A box is lowered at a constant speed

Explanation:

In this question, we're being asked to identify a situation in which no net force is involved.

In order for there to be no net force on an object, then that object must not be accelerating. Hence, we need to look at each answer choice to see if there is any acceleration involved.

For a car that is gradually slowing down, a net force will be involved. This is because the car is undergoing a negative acceleration; it is accelerating in the direction directly opposite to its direction of motion.

In the case of an apple falling from a tree, a net force is also involved. This is because as the apple falls, it is being subjected to the acceleration due to gravity.

A mass attached to a pendulum will also experience a net force. This is because the pendulum is constantly going back and forth, meaning that the direction of acceleration is constantly going back and forth.

Since the motion of a person riding a ferris wheel is circular, there is a continuously changing velocity. Even if speed is kept constant, the direction of motion is always changing, thus the rider experiences a net acceleration and thus a net force.

Finally, a box being lowered at a constant rate will not experience a net force. This is because the box has a constant velocity, which means that no acceleration is involved.

Example Question #57 : Fundamentals Of Force And Newton's Laws

A quarterback throws a football a horizontal distance of  to a wide receiver. The ball was airborne for . The ball had an initial speed of . The ball has a mass of .

If the quarterback’s throw took , determine the average force of the throw.

None of these

Explanation:

Determining horizontal component of velocity:

Using

Solving for

Combining equations

Converting  to

Converting yards to meters

Plugging in values:

Using

Using