Types of Forces
Which statement about the force of gravity is not correct?
a. It acts between all objects that have mass.
b. It is affected by the mass of the objects.
c. It is a contact force.
d. It decreases as the distance between the objects increases
c
If a student decreases the amount of air in the balloon (during a balloon rocket experiment), explain how this would affect the balloon’s distance traveled.
The force pushing the balloon would be less, so the rocket would move a shorter distance down the string.
The force pushing the balloon would be greater, so the rocket would move a shorter distance down the string.
The force pushing the balloon would be greater, so the rocket would move a longer distance down the string.
The force pushing the balloon would be less, so the rocket would move a longer distance down the string.
[Answer: The force pushing the balloon would be less, so the rocket would move a shorter distance down the string.]
40 N <--- 600 ----->
Balanced or Unbalanced?
Unbalanced
When you sit in a chair, you exert a force down on the chair, and the chair exerts a force of (equal/ unequal) strength back up on you.
equal
A metal paper clip lying still on a desk is acted on by multiple forces. When a magnet is brought close to the paper clip, it moves toward the magnet.
Select all options that identify and describe the forces acting on the paper clip.
Friction between the desk and paper clip causes it to stay still before the magnet acts upon it.
Magnetic force between the paper clip and magnet causes the paper clip to be pulled toward the magnet without the need for contact.
Normal contact force between the desk and paper clip before the paper clip is acted on by the magnet.
Gravitational force pulls the paper clip down toward the Earth as it rests on the desk due to its great mass.
[Answer: Magnetic force between the paper clip and magnet causes the paper clip to be pulled toward the magnet without the need for contact.]
[Answer: Normal contact force between the desk and paper clip before the paper clip is acted on by the magnet.]
[Answer: Gravitational force pulls the paper clip down toward the Earth as it rests on the desk due to its great mass.]
Two teams are playing tug-of-war at recess.
The rope is slight going towards group B's side (right side) . How will the forces each group applies to the rope affect its pattern of motion?
Group B is exerting a larger force on the rope than Group A, making the forces unequal and causing the rope to move to the left.
Both groups are exerting equal force on the rope, keeping the rope stationary.
Group A is exerting a larger force on the rope, making the forces unequal, and causing the rope to move to the left.
Group B is exerting a larger force on the rope, making the forces unequal and causing the rope to move to the right.
[Answer: Group B is exerting a larger force on the rope, making the forces unequal and causing the rope to move to the right.]
The student increases the angle of the ramp. How would this affect the force on the race car?
The force on the race car would increase.
The force on the race car would decrease.
The force on the race car would not change.
The race car would not be able to start down the ramp.
[Answer: The force on the race car would increase.]
15.98 N <---- 15.98 ------>
What is the net force?
0 N
According to Newton’s Third Law, what happens when a swimmer pushes against the pool wall to propel themselves forward?
The wall pushes back against the swimmer with the same amount of force.
The wall pushes back against the swimmer with twice as much force.
The wall pushes back against the swimmer with half as much force.
The wall does not push back against the swimmer; the force of the swimmer’s push is what propels them forward.
[Answer: The wall pushes back against the swimmer with the same amount of force.]
Present to the class unbalanced and balanced forces
...
Choose all the examples that demonstrate the force of friction.
A bike rolling down a hill
Rubbing hands together to keep warm
Air rushing over and around a car as it drives down the road
A pot resting on a silicone pad to absorb heat from cooking
[Answer: A bike rolling down a hill]
[Answer: Rubbing hands together to keep warm]
[Answer: Air rushing over and around a car as it drives down the road]
Luis sits in the stationary swing and Jen pushes Luis forward from behind. Explain how this push would change the pattern of Luis’ motion on the swing.
Since the forces on the swing are unequal, the push would increase the swing’s forward momentum
Since the forces on the swing are unequal, the push would decrease the swing’s forward momentum.
Since the forces on the swing are equal, the push would increase the swing’s forward momentum.
Since the forces on the swing are equal, the push would decrease the swing’s forward momentum.
[Answer: Since the forces on the swing are unequal, the push would increase the swing’s forward momentum.]
Tug of war
40 N <--- 600 ----->
What is the net force and is it balanced or unbalanced?
560 N right
Unbalanced
A bucket filled with water exerts a downward force of 200 N and the rope exerts an upward force of 250 N. Calculate the net force, then determine if the forces are balanced or unbalanced and if the system is stable or changing.
50 N Upward unbalanced
A wooden box is sliding down a wooden ramp. Identify and explain how each force acts on the box, as noted by the arrows labeled FA, FB, and FC.
1 pt: The student identifies all three forces accurately.
1 pt: The student explains how the forces are acting on the box.
The data table shows information from an investigation about magnetic force. Pairs of bar magnets were placed end to end at different distances with different poles facing each other.
Magnet Pair , Pole Orientation, Distance Between Magnets
A north and south 4.8 cm
B north and north 20.2 cm
C south and south 10.5 cm
Based on the data, which pair of magnets will repel each other with the greatest magnetic force?
c
After Luis has been swinging for a while, Jen pulls the swing backward with the same force as its motion forward. Explain how this would change the pattern of Luis’ motion.
Since the forces on the swing are equal and in the same direction, the momentum of the swing would increase in that direction.
Since the forces on the swing are equal and opposite, the motion of the swing would stop.
Since the forces on the swing are unequal and in the same direction, the momentum of the swing would increase in that direction.
Since the forces on the swing are unequal and opposite, the momentum of the swing would move in the direction of the greater force.
[Answer: Since the forces on the swing are equal and opposite, the motion of the swing would stop.]
15.98 N <---- 15.98 ------>
Balanced or Unbalanced?
Balanced
Tomás and his younger sister Gwen are finishing work on a wood sculpture. A friend is helping them attach the sculpture to its base. Tomás and Gwen each stand on one side of the sculpture and push on it. They manage to hold it still until their friend finishes attaching the base. Which statement about the forces in this situation is correct?
The forces exerted by Tomás and Gwen are balanced because the sculpture will fall over without a base.
The forces exerted by Tomás and Gwen are balanced because the sculpture remains still.
The forces exerted by Tomás and Gwen are unbalanced because the siblings are not the same age.
The forces exerted by Tomás and Gwen are unbalanced because the sculpture cannot stand on its own.
[Answer The forces exerted by Tomás and Gwen are balanced because the sculpture remains still.]
State Newton’s Third Law of Motion and explain how it would apply to a textbook sitting on a desk. Identify one action-reaction pair of forces at work in your explanation.
1 pt: The student identifies Newton’s Third Law.
1 pt: The student explains how Newton’s Third Law applies to a textbook on a desk.
1 pt: The student identifies simultaneous force pairs at work between two objects.
The table provides definitions for four kinds of forces.
Force Definition
1 Non-contact force that pulls objects toward each other; affected by mass and distance
2 Contact force two surfaces exert when they push or rub against each other; affected by the type of surfaces involved and how hard they are pushed
3 Non-contact force that can be either a push or a pull; direction is dependent on orientation and strength of an object
4 Force exerted on an object by a person or another object
Which option matches each force with its correct position in the table?
1: Gravity; 2: Friction; 3: Applied Forces; 4: Magnetism
1: Magnetism; 2: Gravity; 3: Applied Forces; 4: Friction
1: Gravity; 2: Friction; 3: Magnetism; 4: Applied Forces
3
Exploring Forces
Each sentence describes the effect of a force.
A baseball thrown into the air comes back down again.
A volleyball player spikes a ball over the net.
Water pushing against a swimmer as they move through the water.
A tennis ball comes up from the ground after it is bounced.
The needle in a compass points toward the North Pole.
Which correctly pairs each effect with the force that causes it?
1: Magnetism; 2: Normal; 3: Gravity; 4: Friction; 5: Applied
1: Gravity; 2: Applied; 3: Friction; 4: Normal; 5: Magnetism
1: Applied; 2: Friction; 3: Normal; 4: Magnetism; 5: Gravity
1: Friction; 2: Magnetism; 3: Applied; 4: Gravity; 5: Normal
[Answer: 1: Gravity; 2: Applied; 3: Friction; 4: Normal; 5: Magnetism
A bulldozer is moving rocks in a construction site. Several boulders need to be moved up a hill and away from where the building is being constructed. The bulldozer exerts a force of 800 N, while the boulder exerts an opposing force of 600 N against the bulldozer.
Calculate the net force on the boulder and determine if the forces are balanced or unbalanced.
200 N uphill Unbalanced
According to Newton’s Third Law, what happens when a runner pushes back against the ground to propel themselves forward?
The ground simultaneously exerts the same amount of force on the runner.
The ground simultaneously exerts twice as much force on the runner.
The ground simultaneously exerts half as much force on the runner.
The ground does not exert any force on the runner.
[Answer: The ground simultaneously exerts the same amount of force on the runner.]
According to Newton’s Third Law, what happens when a runner pushes back against the ground to propel themselves forward?
The ground simultaneously exerts the same amount of force on the runner.
The ground simultaneously exerts twice as much force on the runner.
The ground simultaneously exerts half as much force on the runner.
The ground does not exert any force on the runner.
[Answer: The ground simultaneously exerts the same amount of force on the runner.]