Question

mastery check force and momentum
part 1 multiple choice: write the answer that best answers the question in the blank. (1 pt each)

1. which of the laws of motion states, \to every action there is an equal but opposite reaction\?

a. newtons 1st law b. newtons 3rd law
c. newtons 2nd law d. law of conservation of momentum

1. which of the following factors does not affect air resistance?

a. speed b. size
c. spin d. shape

1. which of the following best describes momentum?

a. how much force is needed to change an objects motion
b. how much velocity changes in a given amount of time
c. the tendency of an object to resist a change in motion
d. the balanced forces on a falling object with a constant speed

1. which of the following items has the most inertia?

a. a pencil b. a water bottle
c. your textbook d. the teacher

1. carl and juan are playing catch. carl throws a fastball to juan and it hurts juans hand. why is this the case?

a. greater the acceleration, greater the force b. greater the acceleration, the less the force
c. greater the mass, greater the acceleration d. greater the mass, the less the force

1. a person is on a paddleboard. the person exerts a force on the water with the paddle, causing the water to move. the paddleboard also moves, but in the opposite direction. which statement best explains why this happens?

a. inertia b. newtons 2nd law of motion
c. action and reaction forces d. law of conservation of momentum

1. consider a watermelon that starts from rest and drops straight down from a tall building. air resistance can be ignored. which statement about the watermelons motion is false?

a. the watermelon falls at a constant velocity.
b. the watermelon has a positive acceleration.
c. the watermelons acceleration due to gravity is 9.8 m/s².
d. the watermelon speeds up as it falls.

1. what is the weight (in newtons) of a person with a mass of 95.0 kg?

a. 9.70 n b. 105 n
c. 95.0 n d. 931 n

1. an object has 16 n of force being applied to the right, 16 n of force being applied to the left, and 4 n of force being applied downward. what is the net force on the object?

a. 36 n b. 32 n
c. 4 n downward d. 16 n to the left

1. a 700.0 kg car is driving with an acceleration of 5.0 m/s² down the interstate. what is the force required to accelerate the car?

a. 3,500 n b. 14 n
c. 650 n d. 0.071 n

Explanation:

Step1: Recall Newton's laws

Newton's first law is about inertia (an object at rest stays at rest and an object in motion stays in motion unless acted upon by a force). Newton's second law is \(F = ma\) (force equals mass times acceleration). Newton's third law states that for every action, there is an equal and opposite reaction. The law of conservation of momentum is about the total momentum of a closed system being constant. So for question 1, the answer is B.

Step2: Analyze air - resistance factors

Air resistance \(F_d=\frac{1}{2}
ho v^{2}C_dA\) (where \(
ho\) is air density, \(v\) is speed, \(C_d\) is drag coefficient related to shape, and \(A\) is cross - sectional area related to size). Spin does not directly affect the basic formula for air resistance. So for question 2, the answer is C.

Step3: Define momentum

Momentum \(p = mv\). Option A is related to force (\(F=\Delta p/\Delta t\)), option B is acceleration (\(a=\Delta v/\Delta t\)), option C is inertia (Newton's first law concept), option D is a state of equilibrium. Momentum is mass times velocity. But if we consider the options, none is a perfect definition. However, if we think about the fact that \(F=\Delta p/\Delta t\) (force is the rate of change of momentum), option A is somewhat related in a round - about way (force is needed to change momentum which is related to an object's motion). But if we consider the options again, if we assume a wrong - but - closest - option approach (since the options are not perfect), and if we consider that \(F = ma\) and \(a=\Delta v/\Delta t\), and \(p = mv\), then \(F=\Delta p/\Delta t\). But if we go by elimination: C is inertia (Newton's first law), B is acceleration, D is equilibrium. So the best (though not perfect) is A.

Step4: Inertia and mass

Inertia is directly related to mass. The teacher has the largest mass among the options (a pencil, a water bottle, a textbook, and a teacher). So for question 4, the answer is D.

Step5: Newton's second law application

Using \(F = ma\). For question 8, \(F=mg\) (where \(g = 9.8\ m/s^{2}\)), \(m = 95.0\ kg\), so \(F=95.0\times9.8=931\ N\). For question 10, \(F = ma\), \(m = 700.0\ kg\), \(a=5.0\ m/s^{2}\), so \(F=700\times5=3500\ N\).

Step6: Net - force calculation

For question 9, forces to the right \(F_{right}=16\ N\), to the left \(F_{left}=16\ N\), downward \(F_{down}=4\ N\). The horizontal forces cancel (\(16 - 16=0\) in the horizontal direction), and the net force is \(4\ N\) downward.

Answer:

1. B. Newton's \(3^{rd}\) Law
2. C. Spin
3. A. How much force is needed to change an object’s motion
4. D. The teacher
5. D. \(931\ N\)
6. C. \(4\ N\) downward
7. A. \(3500\ N\)