Investigating Forces

Question 1

A student wants to show that an electric field exists between a charged plastic rod and a small piece of paper, even though the two objects never touch. Which part of the student’s experimental design provides the strongest evidence that a force is acting at a distance?

Accepted Answer

The paper is hung from a string so it can move freely without touching the charged rod.

Answer

The experiment is repeated with the charged rod placed on a metal table to see if the table affects the motion.

Answer

The student records the temperature of the charged rod before and after each trial.

Answer

The student replaces the charged rod with a small magnet and observes whether the paper moves.

Question 2

A 5‑kg block is pulled across a frictionless horizontal surface and accelerates at 2 m/s². What is the magnitude of the net force acting on the block?

Accepted Answer

10 N

Answer

7 N

Answer

2.5 N

Answer

5 N

Question 3

Two forces act on the box as shown by the arrows. What is the net (overall) force on the box?

Accepted Answer

1 unit to the left

Answer

1 unit to the right

Answer

15 units to the left

Answer

8 units to the left

Try three questions

A student wants to show that an electric field exists between a charged plastic rod and a small piece of paper, even though the two objects never touch. Which part of the student’s experimental design provides the strongest evidence that a force is acting at a distance?

A 5‑kg block is pulled across a frictionless horizontal surface and accelerates at 2 m/s². What is the magnitude of the net force acting on the block?

Two forces act on the box as shown by the arrows. What is the net (overall) force on the box?

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