Motion & Forces
Which law states that an object in motion will stay in motion and an object at rest will stay at rest unless acted on by an unbalanced force?
Newton’s First Law
What type of energy is highest when an object is held high above the ground?
Potential energy (gravitational potential energy).
In an action–reaction pair, if object A exerts a force on object B, which force does object B exert? (brief answer)
Object B exerts an equal and opposite force on object A (action–reaction pair).
On a force vs. acceleration graph where lines pass through the origin, what does the slope of each line represent in the relationship between force and acceleration?
Slope represents mass (inverse relation when using F=maF=ma): for a given acceleration, higher slope means larger force per acceleration — equivalently, slope = mass if plotted Force vs. Acceleration.
Name the force that always pulls objects toward Earth.
Gravity
What type of energy increases as an object moves faster?
Kinetic energy.
When a skater pushes a wall and moves backward, which object receives the equal and opposite force from the skater?
The wall receives the force; the wall pushes back on the skater (action–reaction).
From Allison’s paper-clip graph, which answer choice best supports: If Allison added 9 paper clips, the airplane would most likely not fly? (select A, B, C, or D)
D is best: If Allison added 9 paper clips, the airplane would most likely not fly.
If two equal forces act on an object in opposite directions, what is the object's motion (changing speed or not changing speed)? Explain briefly.
Not changing speed because net force is zero when equal opposite forces act; no acceleration.
In the crane diagram, at which labelled position (1 highest, 2, 3, 4 just above the spike) does the ram have the greatest potential energy? Explain briefly.
Position 1 (highest) — greatest gravitational potential energy because height is greatest.
Two bumper cars with different masses collide. Which object (lighter or heavier) tends to have the larger change in motion if they both experience the same force during the collision? Explain with reference to mass and acceleration.
The lighter object tends to experience a larger acceleration for the same force (because a=F/ma=F/m). So lighter mass → larger change in motion given equal force.
A kinetic energy vs. mass scatter plot shows points at (1, 2), (2, 4), and (5, 10). If the object’s speed is constant, what is the relationship between kinetic energy and mass? Predict the kinetic energy for mass 8 kg and choose which plotted point (A–D) matches that prediction. Explain reasoning with the kinetic energy formula. Wrap any numerical expression in your explanation properly.
Kinetic energy is proportional to mass when speed is constant: KE=12mv2KE=21mv2 so for constant vv, KE∝mKE∝m. From points (1,2) and (2,4) we see doubling mass doubles KE → slope is 2 J/kg2 J/kg, so for mass 8 kg expect KE=16 JKE=16 J. Thus option B (point at (8,16)) matches.
On a diagram an object has a 2 N force to the right and a 1 N force to the left. Is the object accelerating? If so, in which direction?
Yes, accelerating to the right because net force = 2 N−1 N=1 N2 N−1 N=1 N to the right.
A skateboard (mass 5 kg) slows when it moves from pavement to grass because the friction force increases. Name the force that explains why the rider keeps moving forward when the board slows.
Inertia (the rider continues forward due to inertia while the skateboard slows from increased friction).
In a model where two riders inside bumper cars have the same mass, what happens to the riders' motion at the moment the cars collide? Choose the best: riders move opposite directions, one moves and one stays, both move together, or something else — explain why using inertia.
The riders (having equal masses) will move because their bodies continue forward relative to the car at impact due to inertia — best model shows riders moving toward the same direction each was traveling (explain with relative motion).
Given three lines on a Force vs. Acceleration graph with equal intercepts at the origin but different slopes, which object has the greatest mass? Explain using Newton’s Second Law.
The object with the greatest mass is the one whose line is steepest (greatest force per acceleration) if force is plotted versus acceleration; slope = mass, so Object 1 (steepest slope) has greatest mass.
A ball accelerates west at 1 m/s2. If one arrow shows a force of 8 N east, what force (in newtons and direction) must act to produce the westward acceleration on a 1 kg? Show reasoning using Newton’s Second Law.
Use Newton’s Second Law F=ma. For a 1 kg ball accelerating west at 1 m/s2, net force must be 1 N west. If 8 N east acts, the westward force must be 9 N west (because 9 N−8 N=1 N west net).
Allison added paper clips to a paper airplane and measured distance flown. From her graph the plane flies farther up to a point, then distance decreases. State one reasonable inference about how mass affects flight distance and explain why adding too many clips could reduce distance using concepts of forces and energy.
Reasonable inference: Increasing mass can increase flight distance up to an optimal point because added mass may increase momentum, but too much mass makes the plane heavier and increases gravitational and drag effects, causing shorter flights. (Matches choice D idea that beyond a point extra mass reduces flight; answer choice in benchmark indicating airplane would not fly with 9 clips supports that inference.)
A car crashes into a wall and crumples. Explain why cars are designed to crumple (use energy and force ideas) and identify which multiple-choice answer from the benchmark best matches that explanation.
Cars crumple to absorb energy during a crash, increasing the time of impact and reducing the force transmitted to passengers. Best matching multiple-choice is B: The wall pushes back with equal and opposite force is related to forces, but the crumple explanation aligns with energy absorption (design uses controlled deformation to reduce force on occupants).
Use the table of 4 objects W, X, Y, Z with horizontal forces shown in the benchmark (W: 1N left, 2N right; X: 2N left, 2N right; Y: 2N right only; Z: 1N left only). Classify which objects have speeds changing and which do not, and explain each classification with net force calculations.
Net force calculations: W = right force (2 N) minus left (1 N) → net = 1 N1 N right → speed changing. X = 2 N left and 2 N right → net = 0 N0 N → speed not changing. Y = 2 N right only → net = 2 N2 N right → speed changing. Z = 1 N left only →