Physics Unit 2: Forces

Physics grade 11 Dynamics - Forces - Fundamental forces - Gravitational field strenght - Force of friction

The force of tension in a rope always acts in the direction of the rope itself.

F (The force of tension can act in various directions, not only along the direction of the rope)

In a FBD, all forces acting on an object must be drawn to scale to accurately represent their magnitudes

F (In a FBD, force are not drawn to scale, instead, they are represented by arrows indicating their directions and magnitudes)

Inertia depends on...

a) an object's weight

b) the force of friction

c) an object's mass

d) the applied force

c) Inertia is proportional to the mass of the object. An increase in mass increases inertia and a decrease in mass decreases inertia.

Kinetic friction is greater than static friction

F, Static friction is greater than kinetic friction as a greater applied force is required for an object to begin moving.

Smooth surface result in higher forces of friction

F, Rough surfaces result in higher forces of friction and smooth surfaces result in lower forces of friction.

Which of the following is a non-contact force?

a. Applied force

b. Electromagnetic force

v. Reaction force

d. Gravitational force

d) (gravitational force is one of the principal non-contact forces we can observe on a daily basis)

The larger the mass of an object, the greater the force required to accelerate the body at a given rate.

T

Sand paper will have a higher force of friction than a glass surface.

T: rough surface finishes result in higher forces of friction than smooth surfaces.

Is the forward force exerted by the skateboard on the skateboarder the reaction force?

T: Newton's third law of motion states that for every action, there is an equal and opposite reaction. When a skateboarder exerts a backward force on the skateboard (action force), the skateboard exerts an equal and opposite forward force on the skateboarder (reaction force).

Does your mass change on each planet in our solar system?

F: Your mass on every plant would be the same because mass does not change with location or gravitational strength. Newton's law of universal gravitation states that the force of gravity between two objects is directly proportional to the product of the masses of the objects and inversely proportional to the square of the distance between their centers.

Friction force is a fundamental force.

F: Friction force is a contact force, it does not fall under the category of fundamental force, which are forces that exist in nature.

Inertia is an objects natural tendency to remain in its current state of motion.

T: Inertia: the natural tendency of an object to remain in its current state of motion. Inertia is directly related to an object's mass. The greater the mass of the object, the greater the inertia.

2. Newton's Second Law of Motion is:

A) An object at rest will remain at rest and an object in motion will remain in motion unless acted upon by an outside force.

B) Fnet=m/a

C) The acceleration of an object is directly proportional to mass and inversely proportional to total force.

D) The acceleration of an object is directly proportional to total force and inversely proportional to mass.

D, Newton's second law is Fnet=m*a which the answer describes.

An object in motion experiences kinetic friction as well as a small, practically negligible, amount of static friction.

F, static friction only applies to an object at rest, and kinetic friction only to an object in motion.

less

FBD stands for Free Body Diagram

T FBD stands for Free Body Diagram

Universal Gravitational constant is 6.67 x 10 nm/kg

F Universal gravity is 6.674×10−11 m3⋅kg−1⋅s−2

Which of the following is the SI unit for weight

A) N

B) lbs

C) kg

D) Fg

A

If an object is at rest or accelerating at a constant velocity the Fnet will not be zero

F- when an object is at rest or accelerating with a constant velocity the net force will always be zero

if the net force on an object increases in the mass is constant the acceleration will increase

T- when you push an object with a greater force it will accelerate faster, if you push the same object with less force it will accelerate slower

when there is an action force there will always be a reaction force that is in the same direction with an equal magnitude

F- When there is an action force there will always be a reaction force with equal magnitude but in the opposite direction

if you are pushing on a desk and it doesn't move. this is due to the force of static friction acting on the desk

T- Static friction is a force that keeps an object at rest

The unit for mass is kg

T

The action force of an object is 13N. What is the reaction force?

A. 13N

B. 12N

C. 27N

D. -13N

D

The formula for calculating the force of gravity on an object is Fg = M x A

F

The formula for calculating the force of gravity acting upon an object is Fg = M x G

Mass is always constant and isn't affected by gravity

T

Mass is constant and isn't affected by gravity, while weight is affected by gravity and thus, isn't constant

A box that has a mass of 7 kg is placed next to a box that's maximum weight is 4 kg in order for neither boxes to move when a person pushes the boxes to the right with an applied force of 24 N. The coefficent of static friction is .22, what is the acceleration of the boxes?

a) .88 m/s^2

b) .80m/s^2

c) 0

d) None of the above

C, if neither boxes are moving, the net force in the x axis is 0, therefore, the boxes will have an acceleration of zero.

Sky divers deploy parachutes to decrease air resistance.

F, sky divers deploy parachutes as they have a large surface area, increasing air resistance to help slow appose the force of gravity, slowing them down.

A car has more inertia than a fox because it can move faster.

F, A car does not have more inertia than a fox because the car is moving faster, it has more inertia than a fox as it has a larger mass.

On neptune you have a very high weight as there is little gravity.

F, on neptune you will weigh the least as the force of gravity is the smallest.

An object that is at rest has no external forces acting upon it.

F, An object at rest may have a net force of zero acting on it. There may be no forces acting upon it, or the sum of all force may equal zero.

If an object is stopped it does not have intertia.

False

Objects always have interia, if they are in motion or not. Due to Newtons 1st law, objects will stay at rest unless acted on by an external force. So that object has interia keeping at rest.

You have the same weight everywhere in the universe.

False

You have the same mass everywhere in the universe. Weight is dependant on the acceleration of gravity where you are measuring (ex. moon, top of mountain, sea level).

Which of the following forces are considered 'fundamental' in nature and physics altogether? (select all that apply)

A. Strong Nuclear Force

B. Tension

C. Weak Nuclear Force

D. Electromagnetic Force

E. Friction

F. Air Resistance

A, C, and D - The correct answers are forces found naturally across the globe. Friction, tension, and air resistance are artificial and can be significantly reduced depending on the mass and position (etc) of an object.

The variable, →Fg is a symbol for the universal gravitational constant, which has a magnitude of 6.67 X 10-11 Nm² /kg²

False - The universal gravitational constant does have a magnitude of 6.67 X 10-11 Nm²/kg², however it is represented by the variable, G. →Fg represents the real-time force of gravity acting on an object measured in Newtons (N).

Which of the following best describes the gravitational force that acts in nature ?

a) The combination of the electrical force between two charged particles at rest and the magnetic force produced when the particles move.

b) The force of attraction between two objects that have mass. The force is calculated using Newton's Law of Universal Gravitation

c) The force responsible for some nuclei being radioactive

d) The force that binds atomic nuclei together.

B

What is newtons second law?

a) The acceleration of an object is directly proportional to and in the same direction as the net force acting upon it and inversely proportional to the body's mass.

b) For every action force on an object B due to object A, there is an equal and opposite reaction force due to object B acting back on object A

c) An object at rest will stay at rest unless acted upon by an external force. An object in uniform motion will continue in uniform motion unless acted upon by an external force

d) None of the above

A

The law or Inertia refers to when an object is at rest it will continue in uniform motion?

F: The law of Inertia refers to when an object is at rest it will stay at rest unless acted upon by an external force

Was Isaac Newton born in 1642?

T: Isaac Newton was born in 1642 and died in 1727

Newton's 1st law states that the greater mass an object has, the greater its inertia and therefore will resist motion to a higher extent.

T - Correct description, as inertia is directly related to an objects mass.

An object with a mass of 12 kg and an acceleration of 7 m/s² has a net force of 84 N.

T - F=ma F=(12kg)(7m/s²) F=84N

Newton's Third law states that for every action force, there is a reaction force with the same magnitude in the opposite direction.

T - Newton's Third law states that for every action force, there is a reaction force with the same magnitude in the opposite direction.

Force of Gravity is equal to the mass divided by 9.81m/s²

F - Force of Gravity is equal to the mass multiplied by 9.81m/s²

A free-body diagram is a vector diagram showing all forces acting simultaneously on an object

T - A free-body diagram is a vector diagram showing all forces acting simultaneously on an object

A book falling from off a desk would have a normal force and force of gravity.

F - A book falling from off a desk would have a force of friction and force of gravity. It would have a friction force and not a normal force because there is air resistance acting on the book.

Which force is responsible for the interactions during

particle transformations?

(a) electromagnetic

(b) gravitational

(c) weak nuclear

(d) strong nuclear

C

Which statement best describes Newton's third law?

(a) For every action force, there is a reaction force of

lesser magnitude and in the same direction.

(b) For every action force, there is a reaction force of

equal magnitude but opposite in direction.

(c) For every action force, there is a reaction force of

equal magnitude and in the same direction.

(d) For every action force, there is a reaction force of

lesser magnitude but in the opposite direction.

B

An ice skater pushes off a railing. Which of the

following is the reaction force?

(a) the force of the skater pushing off the railing

(b) the force of the railing pushing back on the skater

(c) the force of friction from the ice

(d) the force of gravity

B

The normal force is the force resisting the motion or

attempted motion of an object.

F

Massive objects have more inertia than less massive

objects.

T

Which device could be used to measure tension?

(a) a bathroom scale

(b) a balance

(c) a spring scale

(d) a sliding scale

C

One newton is equal to 1 kg·m/s.

F

Forces that do not require contact are called action-

at-a-distance forces.

T

If the net force on an object is constant and the mass

increases, then the acceleration decreases.

T

Which fundamental force is responsible for holding the nucleus of an atom together?

A. Electromagnetic force

B. Gravitational force

C. Strong nuclear force

D. Weak nuclear force

a (According to Newton´s first law of motion, when an object is at rest and not accelerating, the net force acting on it is zero)

When an object is at rest, which of the following is true regarding the net force acting on it?

A. The net force is zero.

B. The net force is always positive.

C. The net force is undefined.

D. The net force is equal to the object's mass.

c (The strong nuclear force is the fundamental force responsible for holding the nucleus of an atom together - it binds protons and neutrons)

The gravitational force between two objects is inversely proportional to the distance between them.

T (According to Newton´s Law of Universal Gravitation, the force of gravitational attraction between any two objects is directly proportional to the product of the masses of the objects, and inversely proportional to the square of the distance between their centres)

The coefficient of friction is always constant for a given pair of materials.

F (The coefficient of friction can vary based on factors like surface roughness, hardness, temperature, etc.)

In Newton´s third law, for every action, there is always an equal and opposite reaction, and these two forces act on the same object.

F (Newton´s third law states that the action and reaction forces act on different objects, not the same)

If Object A exerts a force of 30 N [W] on Object B, what is the force that Object B exerts on Object A?

a) 30 N [W]

b) 30 N [E]

c) 15N [E]

d) Object B does not exert a force on Object A

b) the reactive force is equal in magnitude and opposite in direction to the action force

An object's acceleration is proportional to the object's mass.

F, An object's acceleration is inversely proportional to the object's mass. The larger masses require a greater force to accelerate.

Normal force is always perpendicular to the surface

T, Normal force always points away from the surface.

An object's weight is the same as the object's mass

F, An object's weight is the same as the force of gravity exerted on the object.

An object with a mass of 62 kg on Earth would be which of the following on Saturn?

a. 43 kg

b. 62 kg

c. 89 lb

d. 62 lb

b) (the mass of an object is the same no matter where you are)

The force of gravitational attraction between any two objects is directly proportional to the square of the distance between their centers, and inversely proportional to the product of the masses of the objects.

F (The force of gravitational attraction between any two objects is directly proportional to the product of the masses of the objects, and inversely proportional to the square of the distance between their centers.)

A feather has greater inertia than a truck.

F (A truck has greater inertia than a feather, because the truck's mass is greater than that of the feather.)

The friction decreases as the normal force between two surfaces increases

F (The friction increases as the normal force between two surfaces increases.)

For every action force there is an equal and opposite reaction force.

T

What is earth's mass?

a)9.81 kg

b) 5.98 x 10^24 kg

c) 7.35 x 10^22 kg

d) 598,000,000, 000 kg

B

What factor(s) affect an object's force of gravity?

a) The object's color and shape.

b) The object's velocity and temperature.

c) The object's mass and the distance to other objects.

d) The object's electrical charge and magnetic field.

C

The force of gravity of an object at rest with a static friction of 15N and a coefficient of 0.15 is:

A) 200N

B) 133N

C) 100N

D) 130N

C, the values given can be used to find the normal force (Fn) which is equal to the absolute value of the force of gravity (Fg). It is rounded to one significant figure.

A planet in the Andromeda galaxy experiences a gravitational force from Earth's mass.

T, the fundamental force of gravity has an infinite range, therefore it will experience some force from Earth's gravity but an extremely small, negligible, amount.

The gravitational constant is 6.67 X 10-11 m/s/kg2

F, the gravitational constant is expressed as 6.67 X 10-11 Nm2/kg2

If the net force on an object is zero it must have a velocity of zero and an acceleration of zero.

F, the use of the word 'must' implies that those two conditions need to be met for there to be a total force of zero, however, having a constant velocity that is not zero can also result in that.

If you push a wall the wall does not move, this is explained by Newton's third law of motion.

F, Newton's first law would better explain this, as an object of greater mass will have greater inertia and therefore need more force applied to be in motion.

What are the strongest fundamental forces in nature?

A. Electromagnetic force

B. Gravitational force

C. Weak nuclear force

D. Strong nuclear force

d Strong nuclear force has the strongest fundamental force because, it operates from small range

The unit of weight is:

A. kg

B. N

C. mm

D. km

b) Weight unit is "N" because weight is the force

An object with uniform motion will not continue to move unless there is an external force

F An object with uniform motion will continue to move unless there is a external force

F a on b = -F b on a

T A on B = -F B on A

Kinetic friction is less than Static friction

T Static friction requires more force because object with rest wants to stay at rest and object with moving on constant velocity wants to keep moving unless there is an external force

To calculate the force of gravity you can

A) divide the mass by the acceleration due to gravity

B) divide Fnet by the mass

C) multiply the mass by the acceleration due to gravity

D) multiply mass by the force of friction

C

The mass of an object will change depending on location and gravitational force

F- the only way to change the mass of an object is to add or take away matter

All objects have inertia

T

An object with more mass has more inertia then an object with less mass

T

The mass of an object would be more on Jupiter compared to Earth

F

The net force of an object increases if the mass decreases and the acceleration decreases

F

According to Newton's third law, the reaction force from the thrust produced by a rocket engine would be?

A)In the air

B)On the rocket

C)In the thrust

D)Earth

B

The reaction force would be on the rocket because it's the only positional constant that isn't the thrust itself

Dynamics is the study of the causes of motion

T

Dynamics is the study of the causes of motion

For an object to be at rest vertically, the Normal force must be greater than the Gravity force

F

For an object to be at rest vertically the gravity and normal forces must be equal

According to Newton's first law, an object will continue to accelerate if no forces are acted upon it

F

An object will remain at the same velocity until acted upon, but acceleration is directly proportional to the force acting upon it

The 4 fundamental forces, from weakest to strongest are: gravitational force, weak nuclear force, electromagnetic force, strong nuclear force.

T

Kinetic friction between two surfaces is greater than static friction between the same two surfaces.

F || between the same two forces, static friction will always be greater than kinetic friction because it takes more force to get an object moving and keep it moving, than it does to keep moving an object that is already in motion.

Weight is universal, it does not change regardless of location.

F || mass is universal, doesn't change as location changes. Weight changes as mass/size of planet's surface and acceleration due to gravity change, meaning that your weight on Jupiter is greater than your weight on Earth.

When an small object hits the Earth's surface, no reaction force is felt.

T

Newton is credited with discovering the concept of inertia, and is known as the father of modern physics

F || Galileo Galilei is credited with discovering the concept of inertia. He is known as the father of modern physics, and was a great inspiration to Isaac Newton, who based his findings off of Galileo's work.

A rocket ship is being monitored by astronomers. It is travelling through space at constant speed of 1600 km/hr. How long will the rocket travel until it comes to a complete stop if the astronomer's last recording of the rocket's displacement is 24000000 meters East.

a) 15000 seconds

b) 54000 seconds

c) 600 seconds

d) None of the above

D, the rocket is travelling at a constant velocity in a vaccuum, where no external forces are present, the rocket will therefore never come to a complete stop.

It is easier to move objects once it starts moving due to the coefficent of static friction being greater than the coefficent of kinetic friction.

T, the Coefficent of static friction is greater than the coefficent of kinetic friction, making the friction greater on an object when it is at rest.

The statement "for every action, there is an equal but opposite reaction" is a statment of _____________.

a) Newtons first law

b) Newtons second law

c) Newtons third law

d) One of Newtons Laws

e) None of Newtons Laws

c

Newtons third law is "for every action force on an object B due to object A, there is an equal and opposite reaction force due to abject B acting back on object A."

Whenever a body is in motion, there is always _________ to appose the motion.

a) Friction

b) Inertia

c) Gravity

d) Acceleration

a

When you are moving like running the friction could be air resistance and if you were on standing on a hill there is friction going the opposite way from down the hill.

The acceleration is directly proportional to the the mass.

False

The acceleration is inversely proportional to the mass. Meaning if the mass increases, it will take a higher acceleration to move the object.

Fast moving objects have more interia than slow moving objects of the same mass.

True

Because the object has more mass it is going to take more energy to stop the object from moving because of newtons 1st law. It is much harder to stop a boulder from rolling down a hill than a small rock.