Forces – Study Answers #

1. A force is a push or pull that acts on an object. Forces can change an object’s motion, shape, or direction. Forces are measured in Newtons (N) using devices such as force meters or newton meters.

2. There are two main forces acting on the box:

   • Weight (gravitational force) acting downward
   • Normal reaction force from the table acting upward

   The box doesn’t move because these forces are balanced – they are equal in size but opposite in direction. The normal reaction force from the table exactly balances the weight of the box.

3. The two main forces acting on the football in the air are:

   • Gravity (weight) – pulls the ball downward, causing it to eventually fall to the ground
   • Air resistance – acts in the opposite direction to the motion, causing the ball to gradually slow down

   Initially, when Sarah kicks the ball, its speed is high and air resistance is large. As the ball slows down, air resistance decreases until eventually gravity becomes the dominant force, bringing the ball to the ground.

4. Contact forces require objects to be physically touching each other to have an effect. For example, friction between a car’s tires and the road is a contact force.

   Non-contact forces can act on objects without them touching. For example, gravity is a non-contact force – the Earth can pull on objects without touching them.

5. This statement is incorrect. Balanced forces don’t necessarily mean an object is stationary – they mean there is no change in the object’s motion.

   For example, when a car travels at a constant speed on a flat road, the forces are balanced (driving force equals friction), but the car is still moving. The forces being balanced just means the speed isn’t changing.