Momentum：練習題

Which of the following is a correct unit for momentum?

Why do safety helmets in sports have soft padding inside?

A cannon of mass \(500\text{ kg}\) fires a shell of mass \(10\text{ kg}\) horizontally at a speed of \(200\text{ m/s}\). What is the recoil velocity of the cannon?

An object of mass \(3.0\text{ kg}\) is moving with a velocity of \(5.0\text{ m/s}\).

What is the momentum of the object?

A golf ball of mass \(0.045\text{ kg}\) is hit by a club. The ball is in contact with the club face for \(1.2\text{ ms}\) and leaves the club with a velocity of \(60\text{ m/s}\).

What is the average resultant force exerted by the club on the ball?

Calculate the momentum of a toy car with a mass of \(800\text{ g}\) moving at a constant velocity of \(5.0\text{ m/s}\).

A ball of mass \(0.16\text{ kg}\) hits a wall horizontally at \(10\text{ m/s}\) and rebounds at \(8.0\text{ m/s}\) in the opposite direction. Calculate the magnitude of the change in momentum of the ball during the collision.

Two ice skaters, X and Y, are initially at rest on a frictionless surface. Skater X has a mass of \(60\text{ kg}\) and Skater Y has a mass of \(45\text{ kg}\). They push away from each other. Skater X moves away with a velocity of \(1.5\text{ m/s}\) to the left.

State the total momentum of the skaters after the push and calculate the velocity of Skater Y.

(a) State the equation used to calculate the momentum of an object, identifying the symbols used.

(b) A runner has a mass of \(70\text{ kg}\) and travels at a constant velocity of \(4.0\text{ m/s}\).
Calculate the momentum of the runner and state the correct unit.

A metal sphere of mass \(0.50\text{ kg}\) rolls along a horizontal frictionless track at a constant speed of \(4.0\text{ m/s}\). It collides with a second, identical sphere that is initially at rest. After the collision, the first sphere continues to move in the same direction but at a reduced speed of \(1.2\text{ m/s}\).

(a) Calculate the momentum of the first sphere before the collision.
(b) Using the principle of conservation of momentum, determine the velocity of the second sphere immediately after the impact.
(c) Calculate the magnitude of the impulse exerted on the second sphere during the collision.