Indicate whether the following statements are always true or can be false.
1. If a net force acts on an object, the object's speed will change.
2. If a net force acts on an object, the object's velocity will change.
3. The net force which acts on an object which remains at rest is zero.
4. Two objects are under the influence of equal forces, they have the same acceleration.
5. A motorcycle initially moving at a constant velocity will slow down unless a small net force is applied.
6. Through the collision of a car with a large truck, the car exerts a lesser force on the truck than the truck exerts on the car.