Skip to main content
Ch 08: Momentum, Impulse, and Collisions
Young & Freedman Calc - University Physics 14th Edition
Young & Freedman Calc14th EditionUniversity PhysicsISBN: 9780321973610Non è quello che usi tu?Cambia libro di testo
Capitolo 8, Problema 32

Two skaters collide and grab on to each other on frictionless ice. One of them, of mass 70.0 kg, is moving to the right at 4.00 m/s, while the other, of mass 65.0 kg, is moving to the left at 2.50 m/s. What are the magnitude and direction of the velocity of these skaters just after they collide?

Guida verificata passo dopo passo
1
Identify the principle to use: This is a collision problem on a frictionless surface, so the law of conservation of momentum applies. The total momentum before the collision equals the total momentum after the collision.
Write the equation for the total momentum before the collision: \( p_{\text{initial}} = m_1 v_1 + m_2 v_2 \), where \( m_1 = 70.0 \ \text{kg} \), \( v_1 = 4.00 \ \text{m/s} \), \( m_2 = 65.0 \ \text{kg} \), and \( v_2 = -2.50 \ \text{m/s} \) (negative because the second skater is moving to the left).
Write the equation for the total momentum after the collision: \( p_{\text{final}} = (m_1 + m_2) v_f \), where \( v_f \) is the final velocity of the combined skaters (since they grab onto each other, they move together as one mass).
Set the total initial momentum equal to the total final momentum: \( m_1 v_1 + m_2 v_2 = (m_1 + m_2) v_f \). Solve for \( v_f \) by isolating it: \( v_f = \frac{m_1 v_1 + m_2 v_2}{m_1 + m_2} \).
Substitute the given values into the equation: \( v_f = \frac{(70.0)(4.00) + (65.0)(-2.50)}{70.0 + 65.0} \). Simplify the numerator and denominator to find the final velocity \( v_f \), which gives both the magnitude and direction of the skaters' velocity after the collision.

Risposta video verificata per un problema simile:

Questa soluzione video è stata consigliata dai nostri tutor come utile per risolvere questo problema.
Durata del video:
7m

Concetti chiave

Ecco i concetti essenziali che devi comprendere per rispondere correttamente alla domanda.

Conservation of Momentum

The principle of conservation of momentum states that in a closed system with no external forces, the total momentum before an event must equal the total momentum after the event. In this scenario, the momentum of each skater before the collision must be calculated and summed to find the total momentum, which will then be used to determine their combined velocity after they collide.
Video consigliato:
Percorso guidato
05:58
Conservation Of Momentum

Momentum Calculation

Momentum is calculated as the product of an object's mass and its velocity (p = mv). For the two skaters, their individual momenta must be calculated using their respective masses and velocities. The direction of the momentum is also important, as it indicates whether the momentum is positive or negative based on the chosen coordinate system.
Video consigliato:
Percorso guidato
05:17
Intro to Momentum

Elastic vs. Inelastic Collisions

Inelastic collisions are those in which the colliding objects stick together after the collision, as is the case with the skaters. This type of collision conserves momentum but not kinetic energy. Understanding this distinction is crucial for applying the conservation of momentum correctly to find the final velocity of the combined mass of the skaters after they collide.
Video consigliato:
Percorso guidato
08:56
Intro To Elastic Collisions
Pratica correlata
Domanda del libro di testo

When cars are equipped with flexible bumpers, they will bounce off each other during low-speed collisions, thus causing less damage. In one such accident, a 1750-kg car traveling to the right at 1.50 m/s collides with a 1450-kg car going to the left at 1.10 m/s. Measurements show that the heavier car's speed just after the collision was 0.250 m/s in its original direction. Ignore any road friction during the collision. Calculate the change in the combined kinetic energy of the two-car system during this collision.

1795
views
Domanda del libro di testo

Two ice skaters, Daniel (mass 65.0 kg) and Rebecca (mass 45.0 kg), are practicing. Daniel stops to tie his shoelace and, while at rest, is struck by Rebecca, who is moving at 13.0 m/s before she collides with him. After the collision, Rebecca has a velocity of magnitude 8.00 m/s at an angle of 53.1° from her initial direction. Both skaters move on the frictionless, horizontal surface of the rink. What are the magnitude and direction of Daniel's velocity after the collision?

3521
views
1
rank
Domanda del libro di testo

Two fun-loving otters are sliding toward each other on a muddy (and hence frictionless) horizontal surface. One of them, of mass 7.50 kg, is sliding to the left at 5.00 m/s, while the other, of mass 5.75 kg, is slipping to the right at 6.00 m/s. They hold fast to each other after they collide. How much mechanical energy dissipates during this play?

1572
views
Domanda del libro di testo

Jack (mass 55.0 kg) is sliding due east with speed 8.00 m/s on the surface of a frozen pond. He collides with Jill (mass 48.0 kg), who is initially at rest. After the collision, Jack is traveling at 5.00 m/s in a direction 34.0° north of east. What is Jill's velocity (magnitude and direction) after the collision? Ignore friction.

3023
views
1
comments
Domanda del libro di testo

Two fun-loving otters are sliding toward each other on a muddy (and hence frictionless) horizontal surface. One of them, of mass 7.50 kg, is sliding to the left at 5.00 m/s, while the other, of mass 5.75 kg, is slipping to the right at 6.00 m/s. They hold fast to each other after they collide. Find the magnitude and direction of the velocity of these free-spirited otters right after they collide.

1802
views
Domanda del libro di testo

Two ice skaters, Daniel (mass 65.0 kg) and Rebecca (mass 45.0 kg), are practicing. Daniel stops to tie his shoelace and, while at rest, is struck by Rebecca, who is moving at 13.0 m/s before she collides with him. After the collision, Rebecca has a velocity of magnitude 8.00 m/s at an angle of 53.1° from her initial direction. Both skaters move on the frictionless, horizontal surface of the rink. What is the change in total kinetic energy of the two skaters as a result of the collision?

1551
views