Question

Dan is gliding on his skateboard at 2.00 m/s . He suddenly jumps backward off the skateboard, kicking the skateboard forward at 7.00 m/s (as measured by an observer on the ground). Dan's mass is 40.0 kg and the skateboard's mass is 7.00 kg .

Answer 1

Answer:

The velocity of Dan is 1.13 m/s.

Explanation:

Given that,

Initial velocity of skateboard and Dan = 2.00 m/s

Velocity of skateboard = 7.00 m/s

Mass of Dan m= 40.0 kg

Mass of skateboard M= 7.00 Kg

Suppose How fast is Dan going as his feet hit the ground?

We need to calculate the initial velocity of Dan

Using conservation of momentum

$(m+M)v_{i}=mv_{f}+Mv_{f}$

Put the value into the formula

$(40.0+7.00)\times2.00=40.0\times v_{i}+7.00\times7.00$

$v_{i}=\dfrac{(40.0+7.00)\times2.00-7.00\times7.00}{40.0}$

$v_{i}=1.13\ m/s$

Hence, The velocity of Dan is 1.13 m/s.