Question

1. a 40 n force acts on a 10 kg box. what is its acceleration?

a) 2 m/s²
b) 4 m/s²
c) 10 m/s²
d) 400 m/s²

1. which best represents newtons third law?

a) a runner speeds up when pushing harder against the ground.
b) a soccer ball stays still until its kicked.
c) a toy car keeps moving until it hits a wall.
d) a ball falls because of earths gravity.

1. which formula is correct for speed?

a) force ÷ mass
b) distance ÷ time
c) mass × acceleration
d) velocity ÷ time

1. which of the following is an example of velocity?

a) 10 m/s
b) 50 km/h north
c) 15 seconds
d) 100 kilograms

Explanation:

Step1: Recall Newton's second - law formula

Newton's second - law is $F = ma$, where $F$ is force, $m$ is mass, and $a$ is acceleration. We need to solve for $a$, so $a=\frac{F}{m}$.

Step2: Substitute the given values

Given $F = 40N$ and $m = 10kg$. Then $a=\frac{40N}{10kg}=4m/s^{2}$.

Step3: Recall Newton's third - law concept

Newton's third - law states that for every action, there is an equal and opposite reaction. A runner speeding up when pushing harder against the ground is an example of this. The runner exerts a force on the ground (action), and the ground exerts an equal and opposite force on the runner (reaction), causing the runner to speed up.

Step4: Recall the speed formula

The formula for speed is $v=\frac{d}{t}$, where $v$ is speed, $d$ is distance, and $t$ is time.

Step5: Recall the concept of velocity

Velocity is a vector quantity that has both magnitude and direction. Among the options, $50km/h$ north has both a magnitude ($50km/h$) and a direction (north).

Answer:

1. b) $4m/s^{2}$
2. a) A runner speeds up when pushing harder against the ground.
3. b) Distance $\div$ time
4. b) $50km/h$ north