Question

a net force of 16 n causes a mass to accelerate from rest to 10 m/s in 2 seconds. determine the mass.
a weightlifter can lift a set of 91 kg barbells above his head with an acceleration of 4 m/s². what force does the weightlifter need to apply to the barbells?

Explanation:

Step1: Calculate acceleration

Use the formula \(a=\frac{v - u}{t}\). Here, \(u = 0\space m/s\) (starts from rest), \(v=10\space m/s\), \(t = 2\space s\).
\(a=\frac{10 - 0}{2}=5\space m/s^{2}\)

Step2: Find mass using Newton's second law \(F = ma\)

Given \(F = 16\space N\), \(a = 5\space m/s^{2}\). Rearranging for \(m\), we get \(m=\frac{F}{a}\)
\(m=\frac{16}{5}=3.2\space kg\)

Step3: For the weightlifter problem

Use \(F=m(g + a)\) (where \(g = 9.8\space m/s^{2}\), \(m = 91\space kg\), \(a=4\space m/s^{2}\))
\(F=91\times(9.8 + 4)=91\times13.8 = 1255.8\space N\)

Answer:

For the first problem: \(3.2\space kg\)
For the second problem: \(1255.8\space N\)