A100-kg cannon at rest contains a 10-kg cannon ball. when fired, the cannon ball leaves the cannon with a speed of 90 m/s. what is the recoil speed of the cannon?

Explanation:

Here momentum is conserved,

Initial momentum = Final momentum

Since the system is in rest initially initial momentum is zero,

So we have

               Final momentum = 0

               Momentum of cannon + Momentum of cannon ball = 0

Mass of cannon = 100 kg

Mass of cannon ball = 10 kg

Speed of cannon ball = 90 m/s

               100 x Speed of cannon + 90 x 10 = 0

                100 x Speed of cannon = -900

                Speed of cannon = -9 m/s

The recoil speed of the cannon is 9 m/s

see the picture for the vector

the magnitude of the vector by pythagorean theorem

r = √( (-10)^2 + (3)^2 ) = √109

magnitude = √109 units

the direction angle between vector and x-axis is

tan^(-1)(3/10) = 16.699

so the direction is approximately 16.7 degrees north of west

note: the given question is incomplete.

complete question is given below.

which is an example of kinetic energy?

a. the energy stored in ethanol  

b. a hockey puck sliding across the ice  

c. a compressed spring  

d. a ball sitting at the top of a ramp

solution: the kinetic energy is the energy posses by the virtue of the motion of the object.

in the given options, a, c and d are the example of potential energy because it is the energy posses by the virtue of the rest of the object. but option b has the kinetic energy as the object is in motion.

hence, a hockey puck sliding across the ice   is the apex example of kinetic energy.

so, the option (b) a hockey puck sliding across the ice   is the correct option.