Physics Ch. 2: Kinematics

What is the equation for average velocity?

(v+v₁)/2

What does the sign of the slope on a velocity-time graph indicate?

+ could mean: +speeding up, +to the right, -slowing down, -to the left - could mean: -slowing down, +to the right, + speeding up, -to the left

Two balls are thrown from the top of a 20m tall building. One is thrown upward at 10m/s and the other downward at 10m/s. Determine both of their speeds when they hit the ground

-22.2m/s

When traveling in a circle, what is the displacement?

0

What are the 3 kinematic equations?

1.) v=v₀+at 2.) x=x₀+v₀t+1/2at² →→→ (x-x₀)=v₀t+1/2at² 3.) v²=v₀²+2a(x-x₀)

A ball is dropped from a height of 18m. Determine the time it takes to reach the ground.

1.9s

An object is thrown upward at 50m/s. When 8 s have passed the object's velocity will be closest to...

30m/s downward (up=positive, gravity=negative, answer is negative so velocity must be down)

Two objects starting at rest experience the same uniform acceleration. The second object accelerates for only half the amount of time. How many times greater will the first object's acceleration be?

4

On a planet where the acceleration of gravity is twice that of earth how far will a dropped object fall in 2 s?

40 m

An object at the origin accelerates uniformly from rest. At the end of 1 second the object has displaced 10 m. What is the object's speed after 2 s?

40 m/s

A ball is dropped and falls for 3s. How far does it travel?

44m

What is the acceleration of gravity?

9.8m/s²

An object moving in a circular path completes 1 circumference. Which statements below are true? I. the displacement is zero II. the average speed is zero III. velocity is changing IV. the acceleration is zero

I and III (displacement is 0, velocity is changing)

How do you determine displacement from a velocity-time graph?

displacement=the area under the velocity-time graph

Displacement is a... a.) frame of reference b.) change in position of an object c.) vector magnitude d.) vector direction e.) none of these

e. none of these

Why does someone traveling in a circle have changing velocity?

even if it travelled with constant speed it changed direction as it circled and if either magnitude or direction changes, velocity changes

When a function graphs as a uniform parabola what trick can be used to confer the graph into a linear function?

graphed the squared quantity on an axis

Throw a rock upward and its acceleration...

is the same constant value throughout the flight

What does a velocity-time graph with a displacement of 0 look like?

look for the graph with equal positive and negative areas that will cancel out for zero displacement

What are the units for acceleration?

m/s²

What is deceleration?

negative acceleration; slowing down

What graphs depict constant nonzero acceleration?

position vs. time graph: uniform acceleration appears as quadratic, parabolic velocity vs. time graph: uniform acceleration appears as a line with constant slope; nonzero acceleration could be positive (speeding up) or negative (slowing down)

How do you determine positive velocity and negative acceleration from a velocity-time graph?

positive velocity: positive values for velocity negative acceleration: negative slope

What is the equation for speed?

s=d/t (speed=distance/time)

What does displacement measure?

shortest distance from start to finish

How is acceleration determined from a velocity-time plot?

slope

How is velocity determined from a position-time plot?

slope

What is the equation for time at constant velocity?

t=∆x/v

An object accelerates uniformly from rest reaching a final speed v after traveling a set distance. If it continues to accelerate at the same rate, traveling to a point twice the original distance, its final speed will be...

√2v

What is the slope of a velocity-time graph?

acceleration

If an object passes through the origin and changes direction, what about the variables you're given changes?

acceleration changes sign (+→-, -→+)

Why is a change in speed or direction acceleration?

acceleration involves a change in velocity, which consists of magnitude and direction so if either one changes an object is accelerating

How is velocity determined from an acceleration-time plot?

area=change in velocity; must be added to initial velocity to get current velocity

How is position determined from a velocity-time plot?

area=displacement; must be added to initial position to find current position

Why does someone traveling in a circle have 0 displacement?

because the start is the same as the finish, so the shortest distance from start to finish is 0

Which is not true of acceleration? a. speed can be constant while acceleration b. it is a change in velocity per unit of time c. it is the rate of displacement d. it can be both positive and negative e. it can be a change in speed or direction

c. it is the rate of displacement

Why can acceleration be positive or negative?

can be increasing or decreasing and is a vector with direction

What does a change in slope of a position-time graph indicate?

change in velocity AND change in acceleration

What is the definition of acceleration?

change in velocity divided by time; rate of change in velocity

What does a constant slope on a position-time graph indicate?

constant velocity AND 0 acceleration

What is kinematics?

description of how objects move with respect to a defined reference frame

What does the sign of the velocity value on a velocity-time graph indicate?

direction

How is displacement determined from a velocity-time graph?

displacement=area between the curve and the x-axis; area=∆x (watch the sign); position is found by adding ∆x to x₀

What is the constant velocity equation?

V=∆x/t (velocity=change in displacement/time)

How do the kinematic equations change for freefall?

a becomes g (gravity=9.8m/s²); x becomes y (height instead of length)

On a velocity time graph, how do you know if an object is slowing uniformly?

a uniform (linear) slope that is negative (slowing... velocity numbers decrease)

What is the equation for acceleration?

a=∆v/∆t (acceleration=change in velocity/change in time)

What does distance measure?

total path travelled

True or false: Acceleration is a vector, so direction counts.

true

True or false: gravity is always negative because it points down

true

What do the variables in the kinematic equations represent?

v=final velocity v₀=initial velocity x=final position x₀=initial position t=time a=acceleration

What is the equation for velocity?

v=x/t (velocity=displacement/time)

What is velocity?

vector consisting of both magnitude (speed) and direction; rate of displacement

What is the slope of a position-time graph? What does the sign of the slope indicate?

velocity; direction

When does a velocity-time graph show negative velocity?

when all values for velocity are negative (+x, -y quadrant)

When does a velocity-time graph show positive velocity?

when all values for velocity are positive (+x, +y quadrant)

When is deceleration positive?

when slowing down to the negative side

When does a velocity-time graph show speeding up?

when the number values of velocity get bigger with the line

When does a velocity-time graph show slowing down?

when the number values of velocity get smaller with the line

In freefall problems, when is velocity positive? Negative?

when the thing goes up; when the thing goes down

Under what conditions are average velocity and instantaneous velocity equal?

when velocity is constant

When does velocity equal speed?

when you don't go backward on the x-axis

What is the quadratic formula?

x=-b±√(b²-4ac)/2a

When determining maximum height set final velocity to...

zero