Classical Mechanics
# Introduction to Forces

$m= 4.0 \text{ kg},$ and the slope makes a $\theta=30 ^\circ$ angle with the horizontal. If the cord is cut, what is the magnitude of the acceleration of the block?

In the figure above, a block on a frictionless slope is hanging on a cord. The mass of the block isThe gravitational acceleration is $g= 10 \text{ m/s}^2.$

$900 \text{-kg}$ rocket sled is to be accelerated from rest to $1700 \text{ km/h}$ at a constant rate in $1.8$ seconds in outer space. What is the approximate magnitude of the required net force?

AIn the movie *Spiderman 2*, there's a famous minute long scene where Spiderman stops a train. If the initial speed of a five-car, out of control subway train was around the top speed of the NYC subway (27 m/s), and Spiderman stopped the train in exactly one minute, then what is the magnitude of the force in **Newtons** that Spiderman exerted on the train as he stopped it?

**Details and assumptions**

- A standard New York City subway car full of terrified passengers has a mass of roughly 40,000 kg.
- You may assume the acceleration was constant and any other forces are negligible.

$5$ kg and $3$ kg are hung on a pulley with no friction. Find the magnitude of acceleration $(\text{in m/s}^2 )$ of the left object with mass $5$ kg.

In the above diagram, two objects with their respective massesGravitational acceleration is $g = 10$ m/s$^{2}$.