Some kids are playing by rolling a skateboard across level ground beside a 0.75 m high wall. The goal is to drop from the wall vertically downward onto the skateboard as it passes by. A 45 kg kid manages to land on the 4.5 kg skateboard as it is passing by at 8 m/s, and they move off together horizontally. If the kid is able to stay on, what will be the speed of the kid and skateboard together

The speed of the kid and the skateboard together is 0.723 m/s

Explanation:

Let the mass of the kid be

Let the mass of the skateboard be

The initial speed of the skateboard,

The initial horizontal speed of the boy as he jumps on the skateboard,

Let the speed of the kid and the skateboard together be v

According to the principle of conservation of momentum:

Substituting the appropriate values into  the given equation

36 = 49.8 v

v = 36/49.8

v = 0.723 m/s

the minimum constant speed at which she can catch the train is 2.7 m/s

given:

acceleration = 0.6

time = 4.5 s

to find:

velocity = ?

formula used:

from 1st kinematic equation we get,

v = u + at

u = initial speed of train = 0 m/s

v = final speed of the train

a = acceleration of the train

t = time

solution:

from 1st kinematic equation we get,

v = u + at

u = initial speed of train = 0 m/s

v = final speed of the train

a = acceleration of the train

t = time

v = 0 + (0.6 × 4.5)

v = 2.7 m/s

the minimum constant speed at which she can catch the train is 2.7 m/s