Question

1. a 2 kg object accelerates at 9 m/s². find the net force acting on it.
2. a 4 kg block experiences a net force of 28 n. what is its acceleration?

reflection question:
when solving f = ma problems, why is it important to identify all forces (including friction) acting on an object before calculating?

Explanation:

Step1: Use Newton's second law

Newton's second law is \(F = ma\), where \(F\) is the net force, \(m\) is the mass, and \(a\) is the acceleration.
For problem 24:
Given \(m = 2\space kg\) and \(a=9\space m/s^{2}\).
Substitute into \(F = ma\):
\(F=(2\space kg)\times(9\space m/s^{2})\)

Step2: Calculate the force

\(F = 18\space N\)

For problem 25:
Given \(F = 28\space N\) and \(m = 4\space kg\).
From \(F = ma\), we can solve for \(a\) as \(a=\frac{F}{m}\)
Substitute the values: \(a=\frac{28\space N}{4\space kg}\)

Step3: Calculate the acceleration

\(a = 7\space m/s^{2}\)

For the reflection question:
When solving \(F = ma\) problems, \(F\) is the net force. If we don't identify all forces (including friction), we won't get the correct net force. For example, if there is a frictional force \(f\) acting against the motion and we only consider an applied force \(F_{app}\), the actual net force \(F_{net}=F_{app}-f\). If we ignore \(f\), our calculation of \(F_{net}\) (and thus the acceleration \(a=\frac{F_{net}}{m}\)) will be wrong.

Answer:

1. \(18\space N\)
2. \(7\space m/s^{2}\)

Reflection: To get the correct net force for accurate \(F = ma\) results.