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 #?

1 Answer
Dec 20, 2015

Answer:

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)