Multiple Choice 4

Which of the objects below is accelerating? There might be multiple answers

Slowing down while moving in a straight line

Object moving at constant speed in a circle

Two small balls of the same material, one of mass m and the other of mass 2m, are dropped simultaneously from the Leaning Tower of Pisa. On which ball does Earth exert a bigger force?

On the 2m ball

A baseball is thrown by the pitcher to the second baseman in an attempt to prevent someone from stealing a base. At some point during this process, your friend says that the sum of the forces exerted on the baseball can be described with the equation F=-mg. Which point during the baseball’s motion is your friend referring to?

While the ball is in the air

A person lower’s a 40kg barbell to the ground at a constant velocity at the gym. Which of the following is true about the magnitude of the force the person exerts on the barbell (Fperson on Barbell) and the force Earth exerts on the barbell (Fearth on Barbell)

Fp=Fe

A box of lead and a box of the same size full of feathers are floating inside a spaceship that has left the solar system. They are packed in such a way that you can’t really tell what’s inside by feeling the box. Choose the minimum equipment you would need to compare (not find out exactly, just compare)

A watch with a second hand and a meter stick

A person holds their textbook in one hand and slowly lowers it onto a table at a constant velocity. Which of the following statements is true about the force the person exerts on the textbook?

It points upward and is equal in magnitude to the force Earth exerrts on the book

A book sits on a tabletop. What force is the Newton’s third law pair that Earth exerts on the book? Choose the correct answer with the best explanation

The force that the book exerts on Earth because it describes the same interaction

You are inside an elevator (near the Earth’s surface) standing on a scale. You do not know anything about the motion of the elevator. Which of these forces is guaranteed to always have the same magnitude as the force the elevator exerts on the scale no matter what the elevator is doing? Choose all that apply

The force the scale exerts on the elevator

A 0.10kg apple falls on Earth, whose mass is about 6×10 kg. Which is true of the gravitational force that Earth exerts on the apple?

It is the same magnitude as the force that the apple exerts on Earth

A ping poing ball floats on the surface of a container of water as shown in the image below. Enough time has passed to let the system settle down. What can we say about the magnitude of the force the water exerrts on the ping poing ball (FWater on Ball) and the magnitude of the force Earth exerts on the ping pong ball?

FWater on Ball=FEarth on Ball

A person pushes an 8kg crate, exerting a 64N force on it, but the crate’s acceleration is only 5m/s². Explain

There are other forces exerted on the crate so that the total force is reduced

You push on box G that is next to Box H, causing both boxes to slide along the floor, as shown in the figure baove. The force paired by Newton’s Third Law to the force you exert on box G is

the force that box G exerts on you

Two small balls of the same material, one of mass m and the other of mass 10m, are dropped simulatneously from the Leaning Tower of Pisa. Which is the best statement that describes the situation?

The Earth exerts a larger force on the 10m ball compared to the force it exerts on the 1m ball. However, since the 10m ball has a larger mass than the 1m ball, they accelerate at the same rate

A 20 ton truck collides with a 1500 lb car and causes a lot of damage to the car

the force that the car exerts on the truck due to the collision is exactly equal to the force that the truck exerts on the car

You have two identical books, A and B, each of mass m, on the palm of your hand as shown above. You move your hand upwards with the books, increasing the speed as time goes on. Which of the following is true?

FHand on A>F B on A+mg

The figure shows a graph of the acceleration of an object as a function of the sum of forces acting on it. The mass of this object, in grams, is closest to

130 g

You push on box G that is next to box H, causing both boxes to accelerate along the frictionless floor, as shown in the figure above. Which of the following is true

Fperson on G>Fg on H

Which of the statements below explains why a child lurches forward in a stroller when you abruptly stop the stroller?

The child does not lurch forward but instead continues her motion

A book rests on a table. The book is our system. The force diagram for the book is shown below. In this force diagram, identify the Newton’s 3rd Law pair force to Ft on B

The Third Law Pair show up in the other object’s force diagram

Which vector quantities describing a moving object are always in the same direction?

Acceleration and the sum of the forces

An object is moving forward with a constant velocity. Which statement about this object MUST be true?

The sum of forces on the object is zero

Inside an elevator you are standing on a scale. You have a mass of 60kg. The scale reads 660N. What could be happening? (use g=10 N/kg)

The elevator is moving downards while slowing down at a rate 1 m/s/s

The elevator is moving upwards while speeding up at a rate of 1 m/s/s

A person pushes a 10 kg crate, exerting a 200 N force on it, but the crate’s acceleration is only 5 m/s². Explain

There are other forces exerted on the crate that the total force is reduced

Inside an elevator you are standing on a scale. You have a mass of 66 kg. The scale reads 594 N. What could be happening? (use g=10 N/kg)

The elevator is moving downwards while speeding up at a rate of 1 m/s/s

The elevator is moving upwards while slowing down at a rate of 1 m/s/s

A fish weighing 16 N is weighed using two spring scales. each of negligible weight, as shown in the figure. What will be the readings of the scales?

Each scale will read 16 N

A 7.0 kg object is acted on by two forces. One of the forces is 10.0N acting towards the east. Which of the following forces is the other force if the acceleration of the object is 1.0 m/s² towards the east

3.0 N west

You stand on a bathroom scale in a moving elevator. What happens to the scale reading in the cable holding the elevator suddenly breaks?

The reading will drop to 0 instantly

A physics textbook lies on top of a chemistry book, which rests on a table. Which force diagram below best describes the forces exerted by other objects on the chemistry book?

In an experiment, two carts are equipped with accelerometers and force sensors are sent towards one another with equal velocities and collide. Cart A has twice the mass of cart B. Which of the following statements are true about the magnitude of the force each car exerts on the other and the magnitude of the acceleration of each cart during the collision/

Fa on b=Fb on A

aA<aB

A 1000kg car is driving toward the North along a straight horizontal road at a speed of 20.0 m/s. The driver applies the brakes and the car comes to a rest uniformly in a distance of 200m. What are the magnitude and direction of the sum of forces applied to the car to bring it to rest?

1.00×10³ N southf

Two forces are exerted on an object of mass m in the x direction as illustrated in the unlabeled force diagram below. Assume that these are the only forces acting on the object. Which of the curves labeled A to D on the graph below could be a plot of x(t), the position of the object along the x axis as a function of time?

D

Two forces are exerted on an object of mass m in the x direction as illustrated in the unlabeled force diagram below. Assume that these are the only forces acting on the object. Which of the curves labeled A to D on the graph below could be a plot of vx(t), the velocity of the object in the x direction as a function of time?

B

A book sits on a tabletop. What force is the Newton’s third law pair to the force that table exerts on the book? Choose the correct answer with the best explanation

The force that the book exerts on the table because it describes the same interaction