Forces & Motion Explorer
Push a box across different floors and drop a skydiver with and without a parachute, with the free-body diagram and velocity–time graph computed from the forces.
Learning goals
- Describe the effect of balanced and unbalanced forces on a body
- Describe ways a force may change motion
- Identify action–reaction pairs on interacting bodies
- Draw free-body diagrams for force systems in at most two dimensions
- Apply resultant force = mass × acceleration
Learning objectives
- Describe the effect of balanced and unbalanced forces on a body
- Describe ways a force may change motion
- Identify action–reaction pairs on interacting bodies
- Draw free-body diagrams for force systems in at most two dimensions
- Apply resultant force = mass × acceleration
- Explain the effects of friction on motion
- Describe falling with and without air resistance, including terminal velocity
A 4 kg box on a wood floor pushed with 20 newtons. Friction is 11.8 newtons, the acceleration is 2.06 metres per second squared and the velocity is 0.0 metres per second.
- Friction
- 11.8 N
- Weight, W
- 736 N
- Air resistance
- 0 N
- Resultant force (+ right)
- 8.2 N
- Acceleration, a
- 2.06 m/s²
- Velocity, v
- 0.0 m/s
- Resultant force
- 736 N down
- Acceleration
- 2.06 m/s² down
- Speed
- 0.0 m/s
Try this
0 of 4 donePush the box on the wood floor hard enough to make it slide. (not done yet)
Until the push is bigger than the greatest friction the floor can give, friction matches the push and the forces are balanced.
Keep the box sliding at a steady speed for 2 s on a floor with friction. (not done yet)
A steady velocity needs no resultant force: your push only has to balance friction.
On the smooth floor, get the box moving and then set the push to zero. (not done yet)
With no resultant force the box keeps moving at constant velocity. No force is needed to keep it moving.
Let the skydiver fall fast, then open the parachute and wait for a new steady speed. (not done yet)
Opening the parachute makes air resistance bigger than the weight, so the skydiver slows down until the forces balance at a lower terminal velocity.