Strait Line Motion

Strait Line Motion:

Quickfire Questions (5 min)

1. A car weighing 1kg is accelerating at 2t m/s3 . Find the speed of the car after 5 sec if its initial speed is 6 m/s.

2. A particle moves with velocity V(t) = 2t2 m/s3 . The initial velocity is 1 m/s and initial position is 5 m, find x(t) and a(t).

Example:

A car accelerates from 10 mph to 60 mph in 8 sec. Determine how far the car travels during this time. Constant Acceleration and Freefall:

1. A ball is thrown strait up from x0 with a speed of v0. Draw a(t), v(t), and x(t) for this motion. Label the axis as much as possible. (Aka include vo, x0, xf, etc.)

2. Does a speedometer measure speed or velocity? Explain.

3. Is it possible for an object to be slowing down while its acceleration is increasing in magnitude?

Example:

A diver stands at the top of a 90 m cliff, above the ocean. Determine the velocity of the diver just as he hits the water, ignore air resistance. Projectile Motion:

1. Three balls are launched off a cliff at the same time. (see figure below) In what order do the balls hit the ground?

2. A projectile moves in a parabolic path without air resistance. Is there any point at which a is parallel to v? Perpendicular to v? Explain or Draw.

3. How can a projectile have acceleration when its not moving in the top of its motion?

Example:

A person at the bottom of a small cliff watches as a boulder tumbles off the cliff and move through the air for 3 sec. The person measures that the boulder landed 12 meters from the base of the cliff. How high is the cliff? What was the velocity of the boulder as it rolled off the cliff? Circular Motion:

1. If a pendulum with mass m swings in a circular arc, what is the direction of acceleration at both sides of its movement and in the center?

2. If a person rides in a seat that moves at 20 m/s along a circular path, Determine the acceleration of the person if the radius of motion is 8 meters.

Example:

A 3kg ball is whirled in a vertical circle with a diameter of 160cm. The ball moves with an angular speed ω=90 rpm.

Determine the angular and tangential speed of the ball in units of m/s as it moves.

Determine the centripetal acceleration of the ball during its motion. Work Energy Theorem – Kinetic Energy:

1. Does the kinetic energy of a car change more when it speeds up from 10 m/s to 15m/s or from 15m/s to 10 m/s? Explain.

2. How much Kinetic energy is in a 2kg ball moving at 3 m/s?

3. How are Newton forces related to work? How can you maximize the amount of work a force does on an object?

4. As a ball falls from a height its velocity increases, how does the kinetic energy of the ball change in this movement? If Kinetic Energy changes, where does the energy go or come from?

Example:

A 1.5 kg book beginning at rest has 100N of constant force applied to it. How much work is done in 3 meters of movement?

How fast is it moving after 3 meters of movement? (don’t use kinematics/dynamics)