Question

Den pushes a desk 400 cm across the floor. He exerts a force of 10 N for 8 s to move the desk.

Answer 1

Answer: The correct option is Option b.

Explanation:

Power is defined as the rate of work done by an object.

Mathematically,

$P=\frac{W}{t}$    .....(1)

And work done is the product of force exerted on the object times the displacement covered by that object.

Mathematically,

$W=F.s$

Putting this value in above equation, we get:

$P=\frac{F.s}{t}$

where,

P = power = ?W

F = Force exerted = 10N

s = Displacement = 400cm = 4m   (Conversion factor: 1m = 100 cm)

t = Time taken = 8s

Putting values in above equation, we get

$P=\frac{10\times 4}{8}\\\\P=5W$

Hence, the correct option is Option b.

Answer 2

We Know, P = W/t
P = F * s/t
Here, F = 10N
s = 400cm = 4m
t = 8 sec.

Substitute their values in to expression,
P = 10 * 4/8
P = 10 * 1/2
P = 5 Watt

So, your final answer is 5 W

Hope this helps!