Forces test
A person jumps off of a cliff. While he is falling through the air, how many forces are acting on him?
2
An object sits on the floor and is not moving. How many forces are acting on it?
2
A box is being pushed with a force of 21 N to the north and 51 N to the east. What is the magnitude of a single force that could keep the box from moving?
55N
A force of 5 N and a force of 15 N acting on an object cannot produce which of these net forces: 15N, 5N, 20N, or 10N?
5N
What is friction?
A force that opposes motion between two surfaces that are in contact
These 3 situations describe inertia...
A moving object tends to resist a change in speed. A stationary object tends to resist being moved. A moving object tends to resist a change in direction.
Newton's First Law
An object at rest or in straight-line constant motion will remain at rest or in straight line constant motion unless acted upon by a net external force. ex) car on ice
Newton's Second Law
F=ma, The acceleration on an object is proportional to the net force and inversely proportional to the mass of the object.
Newton's Third Law
For every action force there is an equal and opposite reaction force. ex) rocket taking off
Which of the following statements are true about the concept of field forces? I. Field forces can be exerted by objects that are in physical contact. II. Field forces can be exerted by objects that are not in contact. III. There are four fundamental field forces.
II only
In which situation is the net force acting on a car zero? The car maintains both its speed and direction. The car maintains its speed but changes direction. The car increases speed and changes direction. The car increases speed but does not change direction.
The car maintains both its speed and direction.
What is net force?
The combined forces acting on a particular object
According to Newton's third law, what happens when you push against a wall?
The wall pushes back at you with the same amount of force.
What is true about frictional forces?
They oppose the motion of an object.
field force
a force that is exerted without contact ex) gravity, electrostatic
What is force?
a push or pull on an object
contact force
a push or pull on one object by another that is touching it ex) friction, moving a bookcase
A force unit is defined as the product of a mass unit and a unit of...
acceleration
Two forces act on an object. The magnitude of the net force acting on the object...
cannot be determined from the given information.
The coefficient of friction increases as the mass of an object increases. True or False?
false
An action exerted on an object which may change the object's state of rest or motion defines...
force
Units that measure weight are units of...
force
Accelerations are produced by...
forces
When you push an object across the floor, the force that fights against you is what?
friction
Which 3 things will lead to an increase of sliding friction?
increased mass, increased area, and roughed surface
A box is being moved across a floor by and applied force. A some point a person begins a large rock is placed on top of the box. What happens to the normal force?
increases
A box sits on the floor and you begin pushing on it but it fails to move. As you increase the amount of force you apply the force of friction...
increases to a point
Fnet=
m(kg) x a(m/s2)
Two dogs are tugging on a toy. One dog pulls with a horizontal force of 14 N due north. The other is pulling due east with a horizontal force of 14 N. What is the direction of the net external horizontal force on the toy?
northeast
You are sitting in a chair with wheels and riding in the back of a truck. The Truck suddenly stops. You and your chair will...
roll forward
Which of the following is usually the strongest type of frictional force?
static friction
A box is pushed across a floor with constant speed. In which direction is there a net force?
there is no net force
The frictional force increases as the mass of an object increases. True or False?
true
Ff=
uFn
Is force a vector?
yes, it has magnitude and direction
