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The Snowball Trebuchet: Drop Height and Stored Energy

Grade 8 potential energy practice: campers' snowball trebuchet data model how the counterweight–Earth distance changes stored energy and the throw.

Grade 8ScienceInteractive · Printable

Aligned toMS-PS3-2

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What’s included

Single worksheet
Auto-graded online
1 NGSS standard
Printable answer key
10 questions
Classroom-ready

Details

Format: Interactive · Printable
Grade: Grade 8
Subject: Science
Question types: Fill in the blank, Multiple choice, Sorting, Short answer

About this worksheet

What students practice

Students model how the counterweight–Earth distance changes the potential energy stored in their system.
Students use throw data and a stored-energy rule to compare and predict relative amounts of stored energy.

How to use

Sketch the trebuchet on the board with the bucket raised and lowered, and have students point to the two objects in the system before they start the questions.

Curriculum

NGSS standard covered

MS-PS3-2

Model how changing the distance between interacting objects changes the potential energy stored in the system.

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Name Date

The Snowball Trebuchet: Drop Height and Stored Energy

Model how the distance between a counterweight and Earth changes the energy stored in their system.

The counterweight and Earth

Read the camp notes and Table 1, then answer the questions.

Camp Notes: Building a Snowball Trebuchet

1On the third day of a winter camping trip at Birch Hollow Outdoor Center, the snow was too deep for the planned hike. Trip leader Ms. Simone Arceneaux handed the eighth graders a pile of lumber, a pulley, rope and a sturdy plastic bucket. Their challenge was to build a trebuchet, a throwing machine with a long arm on a pivot. A heavy counterweight hangs from the short end of the arm. When the counterweight falls, the long end of the arm whips up and flings a snowball from a sling. Hundreds of years ago, much larger trebuchets hurled heavy stones at castle walls.

2Campers Wynona Begay and Rafferty Doyle packed the bucket with snow until it had a mass of 12 kg. They used the rope and pulley to raise the bucket and locked the arm with a pin. Ms. Arceneaux pulled the pin for every throw while the campers stood behind a rope line, and the throws landed in an empty, roped-off field. Each snowball had a mass of about 0.2 kg.

3Ms. Arceneaux explained that the bucket and Earth pull on each other, so together they form a system. Energy is stored in this system, and the amount depends on the distance between the bucket and Earth. The drop height is how far the bucket falls from where it is locked to the lowest point of its swing. The camp uses this rule: stored energy (J) compared with the lowest point = mass (kg) × 10 × drop height (m).

4The campers changed the drop height by locking the arm at different marks. For each drop height, they made three throws with the same bucket and snowballs of the same size and measured each throw with a long tape. A few snowballs stuck in the sling and flew sideways; the campers redid those throws and left them out. Table 1 shows the averages. Before the first throw, each camper wrote a prediction in the trip log about how the drop height would change the throw. Later, Rafferty filmed one snowball's flight against a measuring pole to model the snowball–Earth system too.