Question

Can someone explain how to do it or give me a formula for this?

When Isabella pushes a box of mass 5.25 kilograms with a force of 15.7 newtons, it accelerates by a rate of 2.50 meters/second^2. What is the force due to friction in this scenario?

A) -2.60 newtons
B) 5.50 newtons
C) -7.75 newtons
D) 13.5 newtons

Answer 1

With no friction, the acceleration should be:
a=15.7/5.25=3m/sec^2. However the acceleration is 2.5, that means there is an opposite force (friction) whose value is (3-2.5)·5.25=2.6 Newtons. As it goies against the force Isabella is pushing, then negative sign

Answer 2

Hi,
With the use of Newton's second law;
F = ma
where
m = mass
a = acceleration
F = force

= (5.25*2.5)
= 13.125 N
So when 15.7 N is applied the box get affect by 13.125 N which means
1.575 N force has wasted during motion
therefor
F = 1.575 N (friction)