Physics Unit 3: Acceleration

What is the equation for acceleration due to gravity?

vf = vi + a (t)

What is the free fall equation without position?

vf = vi - g (t)

What is the free fall equation with position?

yf = yi + vi t - gt2

Displacement

the change in position of an object

What is the equation for displacement?

delta x= xf-xi

What is the equation for velocity?

velocity = change in displacement / change in time

Velocity

The speed and direction of a moving object

What is the equation for acceleration?

Acceleration = Change in Velocity/Change in Time

Acceleration

The rate of change in the velocity of an object.

Vacuum

no air, nor air resistance.

Does acceleration due to gravity depend on the mass of the falling object?

No

What is air resistance?

friction increases as a falling object's speed increases which reduces acceleration

What is terminal velocity?

Maximum speed an object falls when limited by air resistance

Which kinematic equation would you use to find final velocity vf when you know initial velocity, acceleration, and time?

vf = vi + a (𝛥t)

What are the big 4 kinematic equations?

vf = vi + a (𝛥t)

d = 1/2 (at²) + vi(t)

vf2 = vi2 + 2ad

d= (vf+vi)/2 * t

Which kinematic equation would you use to find displacement (d) when you know initial velocity, acceleration, and time?

d = 1/2 (at²) + vi(t)

Which kinematic equation would you use to find final velocity vf when time is not given, but you know initial velocity, acceleration, and displacement?

vf2 = vi2 + 2ad

Which kinematic equation would you use to find displacement d when you know initial velocity, final velocity, and time?

d= (vf+vi)/2 * t

Acceleration is a ___.

vector quantity

Velocity is a __.

vector quantity

Speed is __.

scalar

When acceleration is in the same direction as velocity, what happens to the object's speed?

The speed increases.

When acceleration is in the opposite direction to velocity, what happens to the object's speed?

The speed decreases.

What is the acceleration if the velocity is changing at a uniform rate?

The acceleration is constant.

If the speed is constant, what is the acceleration?

The acceleration is constant.

If the speed is increasing, what is the acceleration?

The acceleration is constant and positive.

If the speed is decreasing, what is the acceleration?

The acceleration is constant and negative.

How do you calculate displacement of an accelerating object?

Calculate the area under the curve on a velocity-time graph.

For an object in free fall on Earth, what is the acceleration due to gravity?

1000 cm/s/s

A yellow ball with less mass and a black ball with more mass is dropped. Assuming no air resistance, which ball will hit the ground first?

Both at the same time.

A race car has an acceleration of 8 m/s². How long does it take the car to reach a speed of 96 m/s if it starts from rest? Hint: vf=vi+at

12 seconds

A ball is dropped, the initial velocity of the ball is ___.

0 m/s/s

When a traffic light turns green, a car accelerates from rest at 3 m/s2 for 5 seconds. What is the distance covered by the car in that time? Hint: d = 1/2 at² + vi (t)

37.5m

A ball is dropped, at 2 seconds, the velocity of the ball is....

-20 m/s

A cyclist traveling at 19 m/s slams on her brakes and slows down uniformly over 25 meters in 2.2 seconds. What is her acceleration? Hint: d = 1/2 at² + vi (t)

6.9 m/s2

To determine the depth of a well, a rock is dropped into it (from rest). If the rock takes 3.8 seconds to hit the bottom, what is the depth of the well? Use a= 9.8 m/s².

-70.750 m

What is the best way to describe an object in free fall?

The object is affected only by the force of gravity.

A car is traveling at 40 m/s in a straight line. The driver applies the brakes for 4 seconds, and the car slows down to 20 m/s.

−5 m/s2

Which of these describes negative acceleration?

When velocity decreases

A cheetah is walking at 2 m/s when he sees a gazelle. Suddenly he speeds up to 28 m/s. If he accelerated uniformly at 11 m/s2, how many seconds did it take him?

2.36 seconds

A coin is dropped from rest off the Empire State Building. What is its speed right before it hits the ground 381 meters below? Use a = 9.8 m/s2.

86.4 m/s

Based on the motion map shown, describe the object's velocity as a function of time.

The velocity is constant in the negative direction.

Based on the motion map shown, describe the object's velocity as a function of time.

The velocity is constant in the positive direction.

Based on the motion map shown, describe the object's velocity as a function of time.

The velocity is increasing in the positive direction.

An object moving at a constant velocity has an acceleration of:

0 m/s2

Based on the position-time graph, describe the object's velocity as a function of time.

The object is increasing speed in the positive direction.

Based on the position-time graph, describe the object's velocity as a function of time.

The object is increasing speed while moving in the negative direction.

Based on the position-time graph, describe the object's velocity as a function of time.

The object is decreasing in speed while moving in the positive direction.

Based on the position-time graph, describe the object's velocity as a function of time.

The object is decreasing in speed while moving in the negative direction.

Determine the displacement within the first 5 seconds.

12.5 meters