Question

Everyday lighting takes a lot of energy and comparison with sports can be illustrative.

a) How much energy is consumed by a 60 W lightbulb if it’s turned on for only 1 min?

b) If a kicked soccer ball had this much kinetic energy how fast would it be moving in miles per hour?

c) How long would it take a ball moving at this speed to cross the 100m soccer field?

d) Realistically a soccer ball might be kicked at 20m/s. If the kinetic energy of such a ball were used to light the 60 W bulb,how long would the bulb be on?

Answer 1

I am assuming the mass of soccer ball , m = 1kg since it is not given.

a)

power used by lightbulb = P = 60 W

Since power is energy (E) per unit time (1 sec.),

_______________________________ 1

Here P = 60 W and T = 1 min. = 60 sec.

b)

Kinetic Energy ,K of soccer ball of mass m moving with velocity is given by fallowing relation,

__________________________________________ relation 2

So velocity is,

  

this gives

1 meter = 0.000621371 mile and 1 sec = 0.0002778 hour

this gives

C) under assumption of lack of air resistance the ball will travel distance 100 m in in time T as

d) soccer ball kicked with 20 m/s as per relation 2 will have kinetic energy of K =0.5*m*v2 J

K= 0.5*1*400 = 200 J

using relation 1

That amount of energy will power 60 W electric bulb for 3.33 sec