Explore BrainMass

# Mechanics: Force, Collision and Conservation of Momentum

Not what you're looking for? Search our solutions OR ask your own Custom question.

This content was COPIED from BrainMass.com - View the original, and get the already-completed solution here!

A car (m1) is traveling at a velocity (v1) and it smashes into a wall. In situation 1: the car bounces off in a completely elastic collision with no change in speed. In situation 2: the car stops by inelastic collision. Which situation would be the most dangerous. Why?
----------------------------------------------------------------
One of James bond's adversaries is standing on a frozen lake; there is no friction between his feet and the ice. He throws his steel-lined hat with a velocity of 22.0 m/s at 36.9 Degrees above the horizontal, hoping to hit James. If his mass is 120 kg and that of his hat is 4.50 kg, what is the magnitude of his horizontal recoil velocity?

https://brainmass.com/physics/conservation-of-momentum/mechanics-force-collision-conservation-momentum-55848

## SOLUTION This solution is FREE courtesy of BrainMass!

A car (m1) is traveling at a velocity (v1) and it smashes into a wall. In situation 1: the car bounces off in a completely elastic collision with no change in speed. In situation 2: the car stops by inelastic collision. Which situation would be the most dangerous. Why?

The situation one is most dangerous because the change in the linear momentum of the car in situation 1 is (final - initial) = (- m1v1) - (m1v1) = - 2 m1v1 and
in situation 2 it is 0 - m1v1 = - m1v1
so the impulse acting on the car in situation 1 is twice that in situation 2.
----------------------------------------------------------------

One of James bond's adversaries is standing on a frozen lake; there is no friction between his feet and the ice. He throws his steel-lined hat with a velocity of 22.0 m/s at 36.9 Degrees above the horizontal, hoping to hit James. If his mass is 120 kg and that of his hat is 4.50 kg, what is the magnitude of his horizontal recoil velocity?

Consider the hat and the man as a system. As there is no external force acting on the system in horizontal direction, the linear momentum of the system in horizontal direction remains the same.

The horizontal momentum of the system initially is zero as the system is at rest.

The horizontal velocity of the hat after the throw is

vx = v0 cos  = 22.0*cos36.90 = 22*0.8 = 17.6 m/s

if the mass of the hat and the man are m and M respectively then conserving momentum in horizontal direction the velocity v of the man is given by

final momentum = initial momentum
m vx + M v = 0
or v = - m vx /M = - 4.50*17.6/120 = - 0.66 m/s.

The negative sign shows that the man is recoiling in opposite direction.

************************

This content was COPIED from BrainMass.com - View the original, and get the already-completed solution here!