please help with this physics question!!

Question

A 1.2-kg stone is released from rest and falls toward Earth. After 1.8 s, the magnitude of its momentum is:

Answer 1

Momentum = mass* velocity

 

We know the stone's mass = 1.2 kg, so we need to find its velocity.  The stone starts at rest (velocity = 0) and falls under the constant force of gravity, F = mg, where:

• m is the stone's mass = 1.2 kg
• g is the acceleration due to gravity near the Earth's surface = 9.8 m/s²

 

Since the acceleration is constant,, the stone's speed will increase at a constant rate:

 

velocity = acceleration*time = g*t = (9.8 m/s²)*t

 

The stone's momentum at any time t will have a magnitude of:

 

momentum = (1.2 kg)*(9.8 m/sec²)*(t sec.)

 

For t = 1.8 seconds, plug in 1.8 seconds for t.  The units are N*sec or kg*m/s.