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A cartoon shows two friends watching an unoccupied car in free fall after it has rolled off a cliff. one friend says to the other "It goes from zero to sixty miles per hour in about three seconds." is this statement correct?

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AL2006
The acceleration of gravity is 32.2 ft/sec^2.
After 3 seconds of free fall, the car is falling at 96.6 ft/sec.

60 mph is 88 ft/sec.

Let's look at it in two ways:

==> 96.6 is 9.8% greater than 88 .

==> It takes the car (88/32.2)=2.73 seconds to reach 60 mph. 3 is 9.8% greater than 2.73 .

Either way you look at it, the rough number is within 10% of the real number. That's plenty close enough to say that they're "about" the same.

It really depends on what the friends mean when they say "about". As an engineer, my personal feeling is that anything less than 10% off is a beautiful match.

onyebuchinnaji

The statement is not correct because the velocity of the car in a free fall after 3 seconds is 29.4 m/s while the assumed velocity of the friend is 26.82 m/s.

The given information;

  • assumed initial velocity of the car, u = o
  • assumed final velocity of the car, v = 60 miles per hour
  • time of motion, t = 3 seconds

The velocity of an object under the influence of gravity;

v = u + gt

where;

g is acceleration due to gravity = 9.8 m/s²

Convert the given final velocity in mph to m/s;

[tex]v = 60 \ \frac{miles}{hour} \times \frac{1609.34 \ m}{1 \ mile} \times \frac{1 \ hour}{3600 \ s} = 26.82 \ m/s[/tex]

Determine if the assumed final velocity will be equal to actual velocity in 3 seconds after the motion.

v = 0 + (3 x 9.8)

v = 29.4 m/s

Thus, the statement is not correct because the velocity of the car in a free fall after 3 seconds is 29.4 m/s while the assumed velocity of the friend is 26.82 m/s.

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