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:

false br

force is based upon mass and acceleration.the statement is not always true.

it can be explained from newton's second law of motion.

as per newton's second law of motion the rate of change of momentum is directly proportional to the applied force and takes place along the direction of force.

mathematically it can be written as -

                                              ⇒      

here   k is the proportionality constant whose value is 1.

                                                            [a is the acceleration=dv/dt]

hence we see that force not only depends on mass and acceleration but also on velocity and rate of change of mass. force f will depend on mass and acceleration only when mass is constant.

hence the statement that force is based upon mass and acceleration is false.