Question

If you push a 900N refrigerator with the same force as you lift a 40N dumbbell, the dumbbell will move faster. According to Chapter 12, which of Newton’s laws is this an example of? Explain how you know.

Answer 1

Answer:

Second Newton's law

Explanation:

Second Newton's law states that the acceleration of an object is related to the mass of an object and the force applied to it by:

$F=ma$

where

F is the net force applied to an object

m is the mass of the object

a is the acceleration

The equation can be rewritten also as

$a=\frac{F}{m}$ (1)

we see that the acceleration is directly proportional to the force applied, F, and inversely proportional to the mass of the object, m.

In this problem, the force applied to the two objects (refrigerator and dumbbell) is the same, so we must look at their mass. Their mass can be found starting from their weight, which we know:

- refrigerator: $m=\frac{W}{g}=\frac{900 N}{9.8 m/s^2}=91.8 kg$

- dumbbell: $m=\frac{W}{g}=\frac{40 N}{9.8 m/s^2}=4.1 kg$

The dumbbell has a smaller mass, therefore by looking at formula (1), we can see that it will have more acceleration, and this is why it will move faster.