Physics is horrible!?!?

Question

If an 80-kg sprinter can accelerate from a standing start to a speed of 10 m/s in 3 s,
what average power is generated?
(a) 133 W
(b) 267 W
(c) 1330 W
(d) 2667 W

Answer 1

find acceleration
Vf = at + Vi
10 = 3a + 0
a= 3.33m/s^2

find the force
F = ma
F = 80 * 3.33
F = 266N

find the distance
y = 1/2at^2
y = 1/2(3.33)(3)^2
y = 15

power = work /time

power = 266N * 15m / 3s

power = 1330watts

Answer 2

First of all, no subject including Physics is horrible!!! You need to take some interest and of course your teacher needs to be good too.

Let us approach this problem from basics:

Initial speed = 0, final speed after 3 seconds = 10 m/s. Let us assume uniform acceleration. So we use the formula
v = u + a.t and compute a, the acceleration.

10 = 0 + a.3 or a = 10/3 m/sec^2

The runner would have covered a distance of s in this time of 3 secs. The formula for s is v^2 - u^2 = 2 a.s and so s = v^2 / 2a= 10 X 10 X 3 / 2 X 10 = 15 metres.

Now the work done by the man is Force X distance = m.a.s and the average power is work done per second. So, we have

Average power = m.a.s / t
= 80 X 10 X 15 / (3 X 3) = 4000/3 = 1333 watts and is close to answer c given in the question.

See, physics is easy!

Answer 3

Power = force x velocity
= 80*(10/3)*10 = 2666.667 watt
~ 2667 watt

answre is (d).

Answer 4

c

Answer 5

I think it should be the option (c)