Question

1. A drag racer accelerates from rest at 18ft/sec^2. How long does it take to acquire a speed of 60mph? What is required?

Answer 1

(1) The time taken for the drag racer to accelerate is 4.89 s

(2) The speed of the contestant (a) in feet per second is 30.89 ft/s (b) in miles per hr is 21.12 miles per hr.

(1) To calculate the time required to accelerate 18 ft/sec² from rest to a velocity of 60 mph, we use the formula below.

Formula:

• t = (v-u)/a........... Equation 1

Where:

• t = time
• v = Final velocity
• u = initial velocity
• a = acceleration.

From the question,

Given:

• a = 18 ft/sec² = (18×0.3048) = 5.4864 m/s²
• v = 60 mph = (60×0.44704) = 26.82 m/s
• u = 0 m/s ( from rest)

Substitute these values into equation 1

• t = (26.82-0)/5.4864
• t = 4.89 seconds

(2) To calculate the speed of the contestant, we use the formula below

Formula:

• s = d/t............ Equation 1

Where:

• s = speed of the contestant
• d = distance
• t = time.

From the question,

Given:

• d = 100 m
• t = 10.6 s

Substitute these values into equation 1

• s = 100/10.6
• s = 9.43 m/s

(a) In feet = (9.43/0.3048) = 30.94 ft/s

(b)  in miles per hr = (9.43×2.24) = 21.12 miles per hr

Hence, (1) The time taken for the drag racer to accelerate is 4.89 s (2) The speed of the contestant (a) in feet per second is 30.89 ft/s (b) in miles per hr is 21.12 miles per hr.

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