Question

1. a force that opposes motion between surfaces is:

a. normal force
b. gravity
c. friction
d. tension

1. a 4 - kg object experiences a net force of 12 n. its acceleration is:

a. 1 m/s²
b. 3 m/s²
c. 12 m/s²
d. 16 m/s²

1. a person pushes a wall with 50 n. according to newton’s third law, the wall:

a. exerts no force
b. exerts 25 n back
c. exerts 50 n back
d. exerts 100 n back

1. a free - body diagram always shows:

Explanation:

Step1: Analyze question 7

Friction is the force that opposes the relative motion between two surfaces in contact.

Step2: Analyze question 8

According to Newton's second law \(F = ma\), where \(F\) is the net force, \(m\) is the mass and \(a\) is the acceleration. Given \(m = 4\space kg\) and \(F=12\space N\), we can solve for \(a\) as \(a=\frac{F}{m}\). Substituting the values, \(a=\frac{12}{4}=3\space m/s^{2}\).

Step3: Analyze question 9

Newton's third law states that for every action, there is an equal and opposite reaction. If a person pushes a wall with a force of \(50\space N\), the wall pushes back with a force of \(50\space N\) in the opposite direction.

Answer:

1. C. Friction
2. B. \(3\space m/s^{2}\)
3. C. Exerts \(50\space N\) back