Slate, cloth and heat

In the picture

1. 1The green cloth: a tight, smooth surface that lets the ball roll
2. 2The slate slab: a heavy, flat stone layer that stays level
3. 3The heating wire: a thin electric element under the slate
4. 4The billiard ball: a hard round ball moving across the cloth

Examples

• A dry, smooth wooden floor lets a toy car roll farther than a damp, rough carpet.
• A curling stone slides farther on dry, smooth ice than on wet, bumpy ice.

Quiz: Slate, cloth and heat (Age 12)

1. 1

   What do smooth cloth and flat slate do to help a billiard ball?

   • They add dampness, so the ball rolls slower.
   • They make the ball heavier, so it stops sooner.
   • They reduce friction, so the ball keeps moving.
2. 2

   Why does a billiard table have a heater under the slate?

   • To make the slate slab softer and rounder.
   • To make the cloth a darker green.
   • To reduce dampness on the cloth and help the ball roll farther.
3. 3

   What is the slate slab like on a billiard table?

   • A heavy, flat stone layer that stays level.
   • A thin electric element that heats the cloth.
   • A hard, round ball that moves across the cloth.

The answers, each with its explanation, are in the app. This lesson has left the free week, so its quiz is part of the subscription.