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LekaFEV [45]
3 years ago
12

John runs 120 meters in 10 seconds and then runs back to where he started in another 10 seconds. Which statement is true? Rememb

er: speed and velocity mean the same thing. Acceleration is a change is speed over a change in time.
Physics
1 answer:
atroni [7]3 years ago
4 0

Answer:

B

Explanation:

<em>A. His speed is 0 m/s </em>

<em>B. His velocity is 12 m/s </em>

<em>C. His velocity is 0 m/s </em>

<em>D. His acceleration is 12 m/s</em>

Total distance traveled by John = 120 + 120 = 240 meters

Total time taken by John to cover the distance = 10 + 10 = 20 s

<em>Average speed of John = total distance traveled/total time taken</em>

      = 240/20 = 12 m/s

Hence, the average speed/velocity of John throughout the journey is 12 m/s.

The correct option is B.

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Answer:

126.56 m

Explanation:

Applying,

-F = ma............. Equation 1

Where F = frictional force, m = mass of the car, a = acceleration.

Note: Frictional force is negative because it act in opposite direction to motion

But,

F = mgμ.......... Equation 2

Where g = acceleration due to gravity, μ = coefficient of friction

Substitute equation 2 in equation 1

-mgμ = ma

a = -gμ.............. Equation 3

From the question,

Given: μ = 0.735

Constant: 9.8 m/s²

Substitute these values in equation 3

a = -9.8×0.735

a = -7.203 m/s²

Finally,

Applying

v² = u²+2as.............. Equation 4

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From the question,

Given: u = 42.7 m/s, v = 0 m/s (to a stop), a = -7.203 m/s²

Substitute these values into equation 4

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