Pupils can take several approaches to creating a grape smasher. One option is to attach a pulley to the top of a wedge, then attach a heavy block to the pulley. As the pulley moves down the wedge it will drop onto the grapes and crush them. Another option is to roll a wheel and axle over the grape repeatedly until it is crushed.
Depending on the age of your pupils, you can analyze the results in different ways. At very early ages, it makes sense to just eat the remains and leave the results to mystery. For pupils in third grade and up, take a more analytical approach. Have pupils compare and contrast the effects of different weights on the grapes.
Grape smashers for elementary school pupils use simple machines. The six simple machines are the lever, pulley, wedge, screw, inclined plane, and wheel and axle. These machines move objects in ways that elementary science pupils can understand. They are also a good way to start introducing Newton's laws of motion and gravity. Simple machines can also teach historical lessons about how early scientists and engineers built more elaborate machines.
Students in middle school can use the grape smasher project to learn different formulas. For example, force is calculated as mass times gravity: F = mg. Teach students about this equation using the grape smasher project. Measure the weight of the block and find the force of its impact on the grapes. For the wheel, calculate power as torque times angular velocity: P = T X (w).