Trapper stands on a skateboard at rest and throws a 1 kg rock at a velocity of 15 m/s. Trapper moves back at 1 m/s. What is the combined mass of Trapper and the skateboard?

15 kg

Explanation:

We can solve this problem by using the law of conservation of momentum: in fact, in absence of external forces, the total momentum of the (Trapper+skateboard) + rock system must be conserved.

At the beginning, the total momentum of the system is zero, since they are at rest:

The total final momentum is instead:

where:

m = 1 kg is the mass of the rock

v = 15 m/s is the velocity at which the rock is thrown

M is the total combined mass of Trapper and the skateboard

V = -1 m/s is the recoil velocity of Trapper and the skateboard (they move in the opposite direction to the rock)

Since the total momentum is conserved,

Therefore, solving for M, we find the combined mass:

momentum of soft ball three times less than baskey ball

answergravity;