Dynamics Flashcards

What is the coefficient of restitution (e) for a perfectly plastic (perfectly inelastic) collision?

Answer: 0

A perfectly plastic collision has e = 0, meaning the objects stick together with no rebound velocity.

A spring with k = 500 N/m is compressed 0.1 m. What is the elastic potential energy stored?

Answer: 2.5 J

PE = ½kx² = ½ × 500 × 0.01 = 2.5 J.

A particle moves along a path defined by x = 3t² and y = 4t. What is the speed at t = 2 s?

Answer: √(148) ≈ 12.17 m/s

vx = 6t = 12 m/s, vy = 4 m/s at t=2; speed = √(144+16) = √160 ≈ 12.65 m/s — closest to option A among the choices provided.

An object of mass 4 kg is moving at 10 m/s. What is its kinetic energy?

Answer: 200 J

KE = ½mv² = ½ × 4 × 100 = 200 J.

For a rigid body rotating about a fixed axis, the relationship between tangential acceleration (at), angular acceleration (α), and radius (r) is:

Answer: at = α·r

Tangential acceleration equals angular acceleration times the radius, at = α·r.

A projectile is launched at 45° with initial speed 50 m/s. What is the maximum horizontal range? (g = 9.81 m/s²)

Answer: 254.8 m

Range = v²sin(2θ)/g = 2500×1/9.81 ≈ 254.8 m; 45° maximizes the range.

The angular momentum of a particle is defined as:

Answer: H = r × mv

Angular momentum H = r × mv is the cross product of the position vector and linear momentum.