# If a 2 kg object is being constantly accelerated from 0m/s to 15 m/s over  6s, how much power is being applied at t= 3 ?

Dec 20, 2015

P = 19 W

#### Explanation:

To solve this problem we will first find the value of acceleration involved, then use that to determine the resultant force required to produce that acceleration, then find the velocity at 3 s, and lastly calculate the power.

The object has a constant acceleration so the force is constant and the equations of uniform acceleration can be used.

1. Calculate the acceleration.
s =?
$u = 0$
$v = 15 m . {s}^{- 1}$
a =?
$t = 6 s$
Use v = u + at ⇒ a = (v-u)/t
⇒ a = (15-0)/6= 2.5 m.s^(-2)

2. Resultant force.
F=ma = 2× 2.5 = 5.0 N

3. Velocity at 3 s.
We can use an equation of constant acceleration to determine the velocity of the object at 3 seconds.
v= u + at = 0 + 2.5 × 3 = 7.5 m s^(-1)

4. Power.
P = Fv = 5.0 × 7.5 = 37.5 = 38 W (2 sf)