# Worksheet: Force and Pressure

In this worksheet, we will practice defining pressure as the force per unit area and calculating pressures acting on a surface.

Q1:

Why are sharper knives more effective at cutting?

• ASharper knives have smoother surfaces, allowing them to slide into the weak points of what is being cut.
• BThe smaller contact surface of a sharper knife can react faster with the surface of what is being cut.
• CThe sharper the knife, the greater the torque on the cutting surface.
• DSharper knives have smaller contact areas, so, with the same force, this translates to a greater pressure.

Q2:

Why should you roll or belly crawl rather than walk across a thinly frozen pond?

• AThe more of your body rests on the ice, the less you weigh.
• BIf you have more contact with the ice, the ice will warm up and expand, becoming more buoyant.
• CThe greater your contact area with the ice, the lower the pressure and the risk of it breaking.
• DActually, you should walk on tiptoe so that your body heat does not melt the ice.