Force and Motion — Practice Quiz

Its shape changes

Step 1: When equal forces act from opposite sides, they form balanced forces. Step 2: Balanced forces do not cause motion because they cancel each other out. Step 3: However, balanced forces can still change the shape of deformable objects. Step 4: The balloon gets compressed because both forces push inward, changing its shape from round to flattened. Step 5: This demonstrates that balanced forces don't cause motion but can cause deformation in flexible objects.

Newton

Step 1: The SI unit of force is the Newton (N), named after Sir Isaac Newton. Step 2: One Newton is defined as the force that gives a mass of 1 kg an acceleration of 1 m/s². Step 3: From F = ma, we get 1 N = 1 kg × 1 m/s² = 1 kg⋅m/s². Step 4: To feel what 1 N is like, hold a 100g mass in your palm - that's approximately 1 N of force. Step 5: Other units are: kg for mass, Pascal for pressure, and Joule for energy.

Due to inertia of rest

Step 1: Initially, both the bus and passengers are at rest. Step 2: When the bus starts suddenly, the floor moves forward with the bus. Step 3: The passengers' feet, in contact with the floor, also start moving forward. Step 4: However, the upper body of passengers tends to remain at rest due to inertia of rest. Step 5: This causes the passengers to fall backward relative to the bus. This is a classic example of Newton's First Law in action.

Force ÷ Area

Step 1: Pressure is defined as force per unit area, or Pressure = Force ÷ Area. Step 2: This means the same force applied over a smaller area creates higher pressure. Step 3: For example, a nail has a pointed tip to concentrate force over a tiny area, creating high pressure to penetrate wood. Step 4: The SI unit of pressure is N/m² or Pascal (Pa). Step 5: Understanding this helps explain why broad straps are comfortable (distribute force over larger area, reducing pressure) while thin straps are uncomfortable.