Elastic and Inelastic Collisions AP Physics C Mechanics MCQ – Exam Style Questions etc.
Elastic and Inelastic Collisions AP Physics C Mechanics MCQ
Unit 4: Linear Momentum
Weightage : 15-25%
Question
As shown in the top view above, a disc of mass m is moving horizontally to the right with speed v on a table with negligible friction when it collides with a second disc of mass 2m The second disc is moving horizontally to the right with speed v/2 at the moment of impact The two discs stick together upon impact The speed of the composite body immediately after the collision is
(A) v/3 (B) v/2 (C) 2v/3 (D) 3v/2 (E) 2v
Answer/Explanation
Ans:C
Solution: Perfect inelastic collision. m1v1i + m2v2i = mtot(vf) … (m)(v) + (2m)(v / 2) = (3m)vf
Question
A 2 kg ball collides with the floor at an angle θ and rebounds at the same angle and speed as shown above. Which of the following vectors represents the impulse exerted on the ball by the floor?
Answer/Explanation
Ans:E
Solution: Since the angle and speed are the same, the x component velocity has been unchanged which means there could not have been any x direction momentum change. The y direction velocity was reversed so there must have been an upwards y impulse to change and reverse the velocity.
Question
Two balls with masses m and 2m approach each other with equal speeds υ on a horizontal frictionless table, as shown in the top view above. Which of the following shows possible velocities of the balls for a time soon after the balls collide?
Answer/Explanation
Ans:D
Solution: Inspecting the initial approach diagram, it is clear the system has a net monetum to the left (with no vertical momentum). After the collision, the system must still have a momentum to the left with no vertical component. Only one diagram illustrated this possibility.
Question
Cart A of mass 2m is moving with velocity v to the right on a horizontal frictionless track, as shown above, when it collides with cart B of mass m. Cart B is initially at rest, and the collision is perfectly elastic. Which of the following best describes the motion of the carts immediately after the collision?
(A) Cart A is moving to the left, and cart B is moving to the right.
(B) Cart A is moving to the left, and cart B remains stationary.
(C) Cart A is stationary, and cart B is moving to the right.
(D) Both carts move to the right, and they are stuck together.
(E) Both carts move to the right, but they are not stuck together.
Answer/Explanation
Ans:E
For elastic collisions, when an object with a larger mass collides with a stationary object that has a smaller mass, both objects will move in the direction of motion of the first object. In elastic
collision, the objects do not stick together; thus, the carts will move to the right and will not be stuck together.