Question

An object has a mass of 15 kg and is accelerating to the right at 16.3 m/s2. The free-body diagram shows the horizontal forces acting on the object.
What is the frictional force, Ff, acting on the object?

5.5 N
15 N
244.5 N
494.5 N



Answer :
5.5 N

Answer 1

Refer to the free body diagram shown melow.

F =  applied force
R =  frictional force
m = 15 kg, the mass of the object

The acceleration (to the right) is 16.3 m/s², therefore
F - R = (15 kg)*(16.3 m/s²) = 244.5 N

The normal reaction is
N = mg = (15 kg)*(9.8 m/s²)  = 147 N
The frictional force is
R = μN = 147μ N,  where μ =  coefficient of kinetic friction.

Let us check possible answers:
If R = 5.5 N, then μ = 5.5/147 = 0.0374 (very likely)
If R = 15 N, then μ = 15/147 = 0.102 (possible)
If R = 244.5 N,   (Highly unlikely, exceed mg)
If R = 494.5 N, (highly unlikely, exceeds mg)

Answer:
The most reasonable answer is R = 5.5 N

Answer 2

Answer:

Ff = 5.5 N

Explanation:

Given:

M: 15kg

A: 16.3 m/s2

We use:

$f=ma$

force=mass*acceleration

$(15kg)(16.3m/s^{2} )=244.5N$

This means that 244.5 N is the net force on the object, and the right vector is showing 250 N, so to find the left vector - which would be a negative number (left direction) - we do

$(-Ff)+250N= 244.5N (net force)$

Which would give us 5.5 N in the left direction (Ff)

Hope This Helps!