Question

A small 20-kg canoe is floating downriver at a speed of 2 m/s. What is the canoe’s kinetic energy? 80 J 18 J 40 J 400 J

Answer 1

A Physics student on the river bank, watching the canoe float by, says that its kinetic energy is (1/2 m v²) = 40 Joules.

A Physics student in another canoe, floating alongside the first one, says that its kinetic energy is zero.

Both students are correct, each one for his own frame of reference.

Answer 2

The answer is: 40 J.

To solve this problem you must apply the proccedure shown below:

1. You have the following formula that is used to calculate the kinetic energy:

`E_k=(m*V^(2) )/(2)`

Where m is the mass of the objetct and V is the speed.

2. Substitute values into the formula:

`m=20kg\\V=2m/s`

`E_k=((20kg)*(2m/s)^(2) )/(2)`

3. Therefore, the result is:

`E_k=40J`