Sir Isaac Newton was an English mathematician and physicist - Leaving Cert Physics - Question 6 - 2020

Using Newton's second law of motion, the relationship between force and acceleration is: $F = m imes a$ We rearrange to find acceleration: $a = \frac{F}{m} = \frac{-1 ext{ N}}{9 ext{ kg}} = -0.11 ext{ m/s}^2$ This indicates the object is decelerating to the left.

Newton's third law of motion states that for every action, there is an equal and opposite reaction. This means that when one object exerts a force on another, the second object exerts a force of equal magnitude and opposite direction back on the first object.

A rocket takes off by expelling gases downwards at high speed. According to Newton's third law, the force exerted on the gases (action) results in an equal and opposite force exerted on the rocket (reaction), pushing it upwards. A diagram can illustrate the rocket, fuel, and ejected gases.

Kinetic energy (KE) is calculated using the formula: $KE = \frac{1}{2} m v^2$ Substituting the given values: $KE = \frac{1}{2} \times 700 ext{ kg} \times (18 ext{ m/s})^2 = 113400 ext{ J}$

Using the formula for acceleration from Newton's second law: $a = \frac{F}{m}$ The net force is: $F = m \times a \implies a = \frac{F}{m} \text{ where F is } (18 m/s) = \frac{(700 ext{ kg})}{6 ext{ s}} = 3 ext{ m/s}^2$

The net force can be calculated using: $F_{net} = m imes a = 700 ext{ kg} \times 3 ext{ m/s}^2 = 2100 ext{ N}$

The frictional force can be found using: $F_{friction} = F_{engine} - F_{net} = 3000 ext{ N} - 2100 ext{ N} = 900 ext{ N}$

One method of reducing friction is using lubricants, such as oil or grease, which form a film between surfaces to minimize direct contact.