20-kilogram canoe is floating downriver at 2 m/s. what’s the kinetic energy?

40J

Explanation:

Kinetic energy = 1/2 mv^2

Where m = mass and

v = velocity

Given mass = 20kg

v = 2m/s

K.E = 1/2 x 20 x2^2

= 1/2 x 20 x 2 x 2

= 80/2

= 40J

To a physicist floating next to it in another canoe, its KE is zero.

To a physicist standing on the riverbank watching it go by, its KE is 40J.

They're both correct for their own reference frame.

b. false

explanation:

suppose a rock in free fall is dropped off a cliff. after falling for 5 seconds, its speed would not be 100 m/s.