PHYS 001 (Chapter 2)
Homework 2
1. Problem 18 (pg. 53)
Hint:
To remember: When the velocity and acceleration vectors are in the same direction, the
speed of the object increases in time. When the velocity and acceleration vectors are in
opposite directions, the speed of the object decreases in time. The final velocity v is
related to the initial velocity v0, the acceleration a, and the elapsed time t through the
basic definition of average acceleration.
2. Problem 22 (pg.53)
Hint:
Both motorcycles have the same velocity v at the end of the four second interval. Use the
basic definition of average acceleration to find the difference between the initial velocities
of both motorcycles.
3. Problem 34 (pg. 53)
Hint:
The players collide when they have the same x coordinate relative to a common origin.
For convenience, we will place the origin at the starting point of the first player. The
starting point of the second player is 48m away of the origin and the player is moving
towards the first one.
4. Problem 48 (pg. 54)
Hint:
Since the balloon is released from rest, its initial velocity is zero. The time required to fall
through a vertical displacement y can be found from Equation 2.8 from your textbook.
5. Problem 68 (pg. 56)
Hint:
The cheetah and its prey run the same distance. The prey runs at a constant velocity, so
that its distance is the magnitude of its displacement, which is given as the product of
velocity and time. To find the distance for the cheetah can be expressed from the
kinematic equation of motion (Eq. 2.8). Cheetah’s initial velocity and the time are given,
and you will need to determine the acceleration. The two expressions for the distance can
be equated and solved for the acceleration.