Acceleration, Forces, & Newton's Laws Review
One Newton is equal to
1 kg m/s^2
At what rate would a 10 N force accelerate a 1000 g mass?
10 m/s^2
Basking in the sun, a 1.10kg lizard lies on a flat rock tilted at an angle of 15.0 degrees with respect to the horizontal. Draw a free body diagram for this situation. Include friction. Why do we not need to consider air resistance?
25. FBD should include Fg (straight down), Fn (out of the slope), Ff (up the slope). We do not need to consider air resistance because the lizard is not moving
A man is pushing right with 50 N and friction is pushing left with 10 N, what is the net force?
40 N
This measures the rate of change in velocity.
Acceleration
State Newton's first law of motion.
An object at rest remains at rest and an object in motion continues in motion with constant velocity unless it experiences a net external force.
In the equation form of Newton's second law, EF = ma, what does EF represent?
EF is the vector sum of the external forces acting on the object.
True or False: Forces act alone.
False
Another name for a push or a pull.
Force
Cause of acceleration
Force
In a free-body diagram of an object, why are forces exerted by the object not included in the diagram?
Forces exerted by the object do not change its motion.
In a game of tug-of-war, a rope is pulled by a force of 75 N to the left and by a force of 102 N to the right. What is the magnitude and direction of the net horizontal force on the rope?
Given: F1= 102 N, to the right F2= 75 N, to the left Solution Fnet= F1+F2 Fnet= F1-F2= 102 N- 75 N= 27 N Fnet= 27 N, to the right
A wagon having a mass of 32 kg is accelerated across a level road at 0.50 m/s^2. What net force acts on the wagon horizontally?
Given: m= 33 kg a= 0.50 m/s^2 Solution: Fnetyx= EFx= max= (32 kg)(0.50m/s^2)= 16 N
What happens to air resistance when an object accelerates?
In most cases, air resistance increases with increasing speed.
What do we call the sum of the combined forces of an object?
Net force
This law states that objects resist changes in motion unless acted upon by an unbalanced force.
Newton's 1st Law
Which law explains why the dishes do not move during this magic trick?
Newton's 1st Law
Which law uses F=ma to show that acceleration depends on an object's mass and force applied?
Newton's 2nd Law
This law states that for every action, there is an equal and opposite reaction.
Newton's 3rd Law
In what unit of measurement do we express force?
Newtons
Normal force always points...
Perpendicular, away from a surface
Which statement about the acceleration of an object is correct?
The acceleration of an object is directly proportional to the net external force acting on the object and inversely proportional to the mass of the object.
What are the units of the coefficient of friction?
The coefficient of friction has no units
True of False: A force is required to change motion.
True
True or False: Acceleration can be a change in speed or direction or both.
True
True or False: While your body pushes against your chair, your chair also pushed against you.
True
Acceleration is a change in
Velocity
Which are simultaneous equal but opposite forces resulting from the interaction of two objects?
action-reaction pairs
If a nonzero net force is acting on an object, then the object is definitely
being accelerated.
What can forces do?
change an object's speed, change an object's direction, act at a distance
Which of the following forces exists between objects even in the absence of direct physical contact?
field force
Which force acts at a distance?
field, magnetism
What causes a moving object to change direction?
force
Which of the following is the tendency of an object to maintain its state of motion?
force
A free-body diagram represents all of the following except
forces exerted by the object.
Contact force?
friction
What do we call the tendency of objects to resist a change in motion?
inertia
The length of a force vector represents the
magnitude of the force.
A measure of the quantity of matter is
mass.
A crate is released on a frictionless plank inclined at angle 0 with respect to the horizontal. Which of the following relationships is true? (Assume that the x-axis is parallel to the surface of the incline.)
none of the above
Newton's third law of motion involves the interactions of
two objects and two forces.
Which type of force produces an acceleration?
unbalanced force
A change in the gravitational force acting on an object will affect the object's
weight.
The magnitude of the gravitational force acting on an object is
weight.
A car goes forward along a level road at constant velocity. The additional force needed to bring the car into equilibrium is
zero.