Exam 7: Momentum, Collisions, and the Center of Mass

A block of wood with a mass M = 4.65 kg is resting on a horizontal surface when a bullet with a mass m = 18 g and moving with a speed v = 725 m/s strikes it. The coefficient of friction between the block and the surface is µ = 0.35. The distance the block moves across the surface is

Two bodies A and B move toward each other with speeds of 80 cm/s and 20 cm/s, respectively. The mass of A is 140 g and that of B is 60 g. After a head-on, perfectly elastic collision, the speed of B is

A railway car having a total mass of 5.8  10⁵ kg, moving with a speed of 9.1 km/h, strikes another car that has a mass of 8.7  10⁵ kg and is initially at rest. The speed of the coupled cars after the collision is

A bullet mass = m) is fired at speed V into a block of mass M with M > m) which is hanging vertically from a light string of length L. The bullet stops in the block. If the recoiling block + bullet system reaches a height of 2/3L, then the initial speed of the bullet is given by

An automatic rifle fires 0.040-kg projectiles at a speed of 800 m/s. If the gunner holding the rifle in her hands can exert an average force of 160 N against the gun, the maximum number of projectiles she can fire in one minute is

₂. If the pair moves on with velocity , the impulse given the ball of mass m during the collision must have been

A boy and girl on ice skates face each other. The girl has a mass of 20 kg and the boy has a mass of 30 kg. The boy pushes the girl backward at a speed of 3.0 m/s. As a result of the push, the speed of the boy is

In an elastic collision of two objects,

The center of mass of a system of particles is so defined that

A bullet of mass m and velocity strikes and becomes imbedded in a wooden block of mass M, which is initially at rest on a frictionless surface. The ratio of the velocity of the system after collision to the initial velocity of the bullet is

A puck of mass m₁ and initial velocity v₁ collides elastically with a second puck of mass m₂, which is initially at rest. After the collision, m₁ moves with velocity v₁' at an angle below the x axis) and m₂ moves with velocity v₂' at an angle above the x axis). Which of the following statements is true?

Momentum is conserved in which of the following?

Five billiard balls are in contact and at rest on a wire that passes through their centers. Two billiard balls are slammed into one end of the row of five at a velocity . If the balls are free to slide but not roll and if the collision is elastic, which of the following is most likely to take place?

An 1810-kg truck traveling eastward at 64.4 km/h collides at an intersection with a 905-kg automobile traveling northward at 96.5 km/h. The vehicles lock together and immediately after the collision are headed in which direction?

A block that has a mass M = 4.25 kg is hanging at rest on a light string. A projectile with a mass m = 250 g moving horizontally strikes M and sticks to it. The block and its projectile swing up, and the center of mass rises a distance h = 12.0 cm. The speed of the projectile is approximately

A mass m₁ = 2.5 kg is connected to another mass m₂ = 4.0 kg by a compressed spring. Both masses are at rest on a frictionless surface. When the spring is released, the masses are pushed apart and a total energy of 16.8 J is given to the two masses. The speed of mass m₁ is

A bullet with a mass of 20 g and a speed of 960 m/s strikes a block of wood of mass 4.5 kg resting on a horizontal surface. The bullet gets embedded in the block. The speed of the block immediately after the collision

A firefighter uses a hose that shoots water at a rate of 5 m/s and volume flow rate of 40 L/s. If the firefighter is spraying the wall of a house, what is the average force exerted on the wall, assuming that the water splashes sideways in all directions? The density of water is 1000 kg/m³.

Two identical bodies of mass M move with equal speeds v. The direction of their velocities is illustrated above. The magnitude of the linear momentum of the system is

If a body moves in such a way that its linear momentum is constant, then