Describe ways in which a force might change the motion of a body.
- A force is may make
o stationary bodies move.
o moving bodies speed up, slow down or stop.
o moving bodies change direction.
Describe how an object released from rest (subjected to air resistance) will eventually fall with constant velocity.
- Immediately upon release, gravitational force acting on the object causes it to accelerate at 10 m/s2.
- As the object gains speed, the upward air resistance increases. This will cancel out the downward gravitational force and decrease the acceleration.
- Eventually the upward air resistance increases to a point where it equals the downward gravitational force.
- The resultant force acting on the object is now zero. Therefore the acceleration is zero and it continues falling with constant velocity (known as terminal velocity).
Suggest and explain why a car moves at constant velocity after some time even though the car engine continues providing the same amount of forward driving force (thrust).
- During acceleration, the car gains speed and the backward resistive forces (air resistance and contact friction with road) increases.
- It comes to a point where backward resistive forces equals the forward driving force (thrust)
- The resultant force acting on the object is now zero. Therefore the acceleration is zero and it continues moving with constant velocity (known as terminal velocity).