Question

How long will it take a 250-N box initially at rest reach a speed of 36 km/h when a force of 65 N is applied on it? The floor is frictionless.

O 1.2 S

O not among the choices

O 2.3 s

O 4.5 s

O 3.9 S

Answer 1

Given:

$W=250\:\rm N$

$F=65\:\rm N$

$\Delta v=36\:\rm km/h=10\: m/s$

$\Delta t-?$

The Newton's second law says

$$ma=F$$

Hence, the acceleration of the object

$$a=\frac{F}{m}=g\frac{F}{W}=\rm 9.8*\frac{65}{250}=2.55\: m/s^2$$

The time of movement

$$\Delta t=\frac{\Delta v}{a}=\frac{10}{2.55}=3.9\:\rm s$$

Answer: $3.9\:\rm s$