Momentum: Ice skater throws a ball | Impacts and linear momentum | Physics | Khan Academy

TL;DR

An ice skater throws a ball forward with a speed of 35 m/s and a mass of 0.15 kg. The skater's recoil velocity is calculated to be approximately -0.105 m/s.

Transcript

Welcome back. I'll now do a couple of more momentum problems. So this first problem, I have this ice skater and she's on an ice skating rink. And what she's doing is she's holding a ball. And this ball-- let me draw the ball-- this is a 0.15 kilogram ball. And she throws it. Let's just say she throws it directly straight forward in front of her, al... Read More

Key Insights

• 🟰 The conservation of momentum applies to this problem, where the initial momentum is equal to the final momentum.
• 💆 The momentum of an object is calculated by multiplying its mass with its velocity.
• 💬 The skater's recoil velocity is in the opposite direction of the thrown ball's velocity.

Questions & Answers

Q: What is the initial momentum of the system?

The initial momentum of the system is 0, as both the skater and the ball are stationary before the throw.

Q: What is the momentum of the ball after being thrown?

The momentum of the ball is calculated by multiplying its mass (0.15 kg) with its velocity (35 m/s), resulting in a momentum of 5.25 kg*m/s.

Q: What is the momentum of the skater after the throw?

Since momentum is conserved, the momentum of the skater is equal to the negative momentum of the ball, which is -5.25 kg*m/s.

Q: What is the recoil velocity of the skater?

The recoil velocity of the skater is calculated by dividing the momentum of the skater (-5.25 kg*m/s) by the skater's mass (49.85 kg), resulting in a velocity of approximately -0.105 m/s.

Summary & Key Takeaways

• An ice skater throws a 0.15 kg ball forward with a velocity of 35 m/s.

• The combined mass of the skater and the ball is 50 kg.

• Using the conservation of momentum, the skater's recoil velocity is calculated to be approximately -0.105 m/s.