PhysicsLAB: Test Scenario: 2nd and 3rd Law Forces

Worksheet
Test Scenario: 2nd and 3rd Law Forces

This page is based on a Conceptual Physics Practice Page that dealt with static equilibrium.

Refer to the following information for the next eight questions.

A uniform plank supports Burt the painter with normal force, N, which acts in a direction opposite to his weight, W.

We can say N

equals W

has the same magnitude as W

Since Burt is at rest, the net force on him is

nonzerozero

The above answer is true because N and W are

2nd Law Forces3rd Law Forces

N is equal and opposite to W. We ___ say that N and W comprise an action-reaction pair.

cancannot

The reason is because action and reaction always

act on the same objectact on different objects.

and here we see that N and W

are both acting on Burtare acting on different objects

In accordance with the rule, "If the ACTION is A acting on B, then the REACTION is B acting on A," if we say that the action is the earth pulling down on Burt, then the reaction is

the plank pushing up on BurtBurt pulling up on the Earth

To summarize, we see that N and W are equal and opposite to each other

and comprise an action-reaction pair.but do not comprise an action-reaction pair.