Question

Questions:

1. What is the distinction between “speed” and “Velocity”? Describe.

2. What is the relationship between velocity and acceleration?

How does the velocity and acceleration of a free falling object change with time?

Problems:

The distance between the moon and earth is about 3.8x108 How long it will take for a laser beam of light to travel from earth to moon and back to the earth (round-trip)?

Note: laser is traveling at speed of light.

2. A car can go from 0 to 100 mph in 7.9 seconds. Calculate the car’s average acceleration in m/s2.

3. During a rainy day, as a result of colliding clouds an observer saw lighting and a heard thunder sound. The time between seeing the lighting and hearing the sound was 5 second. Calculate the distance of the colliding cloud from the observer.

A baseball is thrown vertically upward at a speed of 39.2 m/s. How much time elapsed before it reaches it highest points, and how high above the ground does it get?

Answer 1

Questions:

1. Speed is scalar quantity. measures how fast a object is moving.

velocity is vector which also has direction and whose magnitude is speed.

2. a = rate of change of velocity

a = dv/dt

acceleration remains constant as 9.8m/s^2 downward.

Speed increases in downward ( v = 9.8 t downward)

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t = 2(3.844 x 10^8) / (3 x 10^8)

t = 2.56 sec  

2. vf = 100 x 1609 m / 3600s = 44.7 m/s

a = (vf - vi) / t = (44.7 - 0) / 7.9 = 5.66 m/s^2