Question

1. A curious physics student drops a book from a high building.

A. What is the VELOCITY of the brick after 3.0s?
B. How FAR(Distance) does the book fall during this time?

2. Suppose a free-fall ride at an amusement park starts at a rest and then drops.
A. What is the VELOCITY of the ride after 2.5s?
B. How FAR do people on the ride fall during the 2.5s time period?

3. You throw a ball downward from a window at a speed of 3.0 m/s.
A. How FAST will it be moving when it hits the sidewalk 2.0m below?

4. If I drop a photo copier off of a 45m tall building and splats on the ground below:
A. Calculate the TIME to hit the ground:
B. Calculate the VELOCITY just before:

Answer 1

1.

A. Vf = 29.4 m/s

B. h = 44.1 m

2.

A. Vf = 24.5 m/s

B. h = 30.625 m

3.

A. Vf = 5.5 m/s

4.

A. t = 3.03 s

B. Vf = 29.7 m/s

Step-by-step explanation:

1.

A.

using 1st equation of motion:

Vf = Vi + gt

where,

Vf = Final Velocity = ?

Vi = Initial Velocity = 0 m/s (since, book starts from rest)

g = 9.8 m/s²

t = time = 3 s

Therefore,

Vf = 0 m/s + (9.8 m/s²)(3 s)

Vf = 29.4 m/s

B.

using 2nd equation of motion:

h = Vi t + (1/2)gt²

h = (0 m/s)(3 s) + (1/2)(9.8 m/s²)(3 s)²

h = 44.1 m

2.

A.

using 1st equation of motion:

Vf = Vi + gt

where,

Vf = Final Velocity = ?

Vi = Initial Velocity = 0 m/s (since, book starts from rest)

g = 9.8 m/s²

t = time = 2.5 s

Therefore,

Vf = 0 m/s + (9.8 m/s²)(2.5 s)

Vf = 24.5 m/s

B.

using 2nd equation of motion:

h = Vi t + (1/2)gt²

h = (0 m/s)(2.5 s) + (1/2)(9.8 m/s²)(2.5 s)²

h = 30.625 m

3.

A.

using 3rd equation of motion:

2gh = Vf² - Vi²

where,

Vf = Final Velocity = ?

Vi = Initial Velocity = 3 m/s

g = 9.8 m/s²

h = height = 2 m

Therefore,

2(9.8 m/s²)(2 m) = Vf² - (3 ms)²

Vf² = 39.2 m²/s² - 9 m²/s²

Vf = √30.2 m²/s²

Vf = 5.5 m/s

4.

A.

using 2nd equation of motion:

h = Vi t + (1/2)gt²

where,

h = height = 45 m

Vi = Initial Velocity = 0 m/s (since, photo copier was initially at rest)

t = time = ?

g = 9.8 m/s²

45 m = (0 m/s)(t) + (1/2)(9.8 m/s²)(t)²

t² = 2(45 m)/(9.8 m/s²)

t = √9.18 s²

t = 3.03 s

B.

using 1st equation of motion:

Vf = Vi + gt

Vf = 0 m/s + (9.8 m/s²)(3.03 s)

Vf = 29.7 m/s