Question

A penny is dropped from the top of a building 290 m high. Ignoring air resistance, if

the penny falls straight down, with what speed would it hit the ground?

In the above experiment, identify two reasons why the speed with which the penny
hits the ground may not be exactly what is calculated and predicted.

Answer 1

1. Velocity = 75.39 m/s

2. Air resistance

3. Mass of the coin

Step-by-step explanation:

1. Given that the height of the building is 290 m. From Newton's third law of motion,

`V^(2)` =
`U^(2)` + 2gh

where: V is the final velocity of the coin, U is the initial velocity, g is the force of gravity and h is the height.

Since the coin was dropped from a height, its initial velocity is zero. The force of gravity is taken as 9.8 m/
`s^(2)`, so that:

`V^(2)` = 0 + 2 x 9.8 x 290

= 5684

V =
`√(5684)`

= 75.3923

The velocity with which the coin hits the ground is 75.39 m/s.

2. Air resistance: During the free fall of the coin, the direction of wind flow could either cause an increase or decrease the value predicted.

ii. Mass of the coin: This can also affect the predicted value.