Unit 5 - Collisions - AP Physics

In order to determine motion of two objects after they collide you must know

• the motion before they collide.

• know which direction they are moving.

• that they are at rest

• their mass only.

Mechanical energy is conserved only when objects

• stick together.

• bounce off each other.

• start from rest.

• are moving very fast right before the collision.

Momentum is conserved

• always.

• in elastic collisions.

• in inelastic collisions.

• any of these will work.

Consider 2 cars moving at different speeds and then they collide. We do not know if they stick together or bounce off each other. What can we determine about the speed of the 2 car system after the collision?

• The speed of the system remains the same.

• The speed slows down if they stick together and speeds up if they bounce off.

• The speed slows down if they bounce off each other and speeds up if the stick together.

• Mechanical energy stays the same.

A force acted upon an object for 3 s as shown in the graph below.
What is the magnitude of the impulse on the object?

• 3
• 4.5
• 6
• 9

A 10kg toy truck moves at 5m/s East. It collides and bounces off of a 5kg toy car moving 10 m/s moving west. Which equation would you use to solve for the final velocity of the car?

• m₁v_1i+m₂v_2i=m₁v_1f+m₂v_2f
  
• (m₁+m₂₎v_i=m₁v_1f+m₂v_2f 
• m₁v_1i+m₂v_2i=(m₁+m₂)v_f

Tags

NGSS.HS-PS2-2

The graph shows the force on an object of mass M as a function of time. For the time interval 0 to 4 s, the total change in the momentum of the object is

• 40 kg m/s 
• 20 kg m/s
• 0 kg m/s 
• – 20 kg m/s

What is Newton's 2nd Law of Motion?

• Action - Reaction. If an object A exerts a force on object B, then object B must exert a force of equal magnitude and opposite direction back on object A.

• F = ma. An object acted on by an unbalanced force will accelerate in the direction of that force, in direct proportion to the strength of the force, and in inverse proportion to the mass of the object.

• Inertia: An object in motion tends to stay in motion, while an object at rest tends to stay at rest unless acted upon by an unbalanced force.

Check ALL that apply.

Impulse is:

• The force that creates an acceleration.

• The change in momentum.

• the change in velocity that can be caused by a constant force over some discrete amount of time.

• A vector

• NOT a vector

The impulse is ______ the change in momentum

• greater than
• equal to
• less than
• always double