Answers to physics problems

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To answer some basic physics problems we need to remember some basic formulas that will be very helpful.
                   s = vt
                   s = ut + ½ at^2
                   v = u + at
                   v^2 = u^2 + 2as
                   a = v/t         and
                   a = (v-u)/t

Question: A car is accelerating at 25 m/S^2.  Find its acceleration in Km/h^2.

Answer:  We know that, 1 m = 0.001 km
                   And 1 sec = 1/3600 hr
          So that, we can write,
                             25 m/s^2 = 25(0.001)(3600)^2 = 324000 km/h^2.
 

Question: How high can a human throw a ball if he can throw it with initial velocity 70 Km/h?

Solution: Given that,
          Initial velocity, u = 70 km/h = 70(1000)/3600 = 19.44 m/s
          Final velocity, v = 0 m/s because ball will be stopped at the highest point.
          Acceleration due to gravity, g = 9.8 m/s^2
We need to find the vertical distance that is height, h
And we can use the formula
                   v^2 = u^2 + 2as
                   0^2 = (19.44)^2 + 2(9.8)h
                   h = 19.28 m.

Question: It takes you 5 minutes to walk with an average velocity of 4.5 m/s to the north from the bus stop to museum entrance. What is your displacement?

Solution: Given that,
                   Velocity, v = 4.5 m/s
                   Time, t = 5 min = 5x60 = 300 sec
          Now, we have the equation for displacement
                             s = vt
                               = 4.5(300) = 1350 m
 
 

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