Homework Solutions 1
Physics 121, Section 1
Due 9/6/07
In the rst two problems of this solution, I have included the full level of
detail I would expect to see in your solutions. In the nal problem and on
subsequent assignment, we will usually only includ
Homework Solution 7
Physics 121, Section 1
Due 10/2/07
1. (a) Why do you fall backward when standing inside a bus which is accelerating from rest?
As the bus accelerates forward, your body tends to follow Newton's First Law and not
accelerate. Thus, in an
Homework Solution 2
Physics 121, Section 1
Due 9/11/07
1. Wilma I. Ball walks at a constant speed of 4.83 m/s from home to the pharmacy to pick up her
prescription. She then walks back home along the same route with a constant speed of 3.66 m/s;.
What is
Homework Solution 10
Physics 121, Section 1
Due 10/11/07
1. The loaded car of a roller coaster has mass m = 320 kg. It goes over the top of a `hill' with a speed v
of 20 m/s. The radius of curvature R of the hill is 15 m.
(a) What are the magnitude and di
Homework Solution 9
Physics 121, Section 1
Due 10/9/07
1. A block with a mass of M = 7.65 kg is initially moving up the incline and is increasing speed with
a = 1.44 m/s2 . The applied force F is horizontal. The coecients of friction between the block and
Homework Solution 8
Physics 121, Section 1
Due 10/4/07
1. A block starts from rest at the top of a d = 2.00-m long, = 38.0 frictionless incline.
(a) What is the acceleration of the block?
Solution: Let the x direction be down the incline. The y direction
Homework Solution 6
Physics 121, Section 1
Due 9/25/07
1. Work out the physics of the Monkey Hunter demonstration we did in class on Tuesday, September 20.
Assume that a projectile is shot from a blow gun at the same time a monkey drops from rest by letti
Homework Solution 5
Physics 121, Section 1
Due 9/20/07
1. What is wrong with the physics in the following statement? The car rounds the turn at a constant
velocity of 50 km/h Rewrite it so that it conveys the correct meaning.
Solution: If the car is round
Homework Solution 4
Physics 121, Section 1
Due 9/18/07
1. Joan measures the distance across a straight river by the following method:
Starting directly across the river from a tree on the opposite bank, she
walks 106 m along the river bank to establish a
Homework Solution 3
Physics 121, Section 1
Due 9/13/07
1. Eric slams on the brakes when he sees a tree blocking the road. The
car slows uniformly with an acceleration of -5.12 m/s2 for 3.51 s, making
straight skid marks 61.4 m long ending at the tree. Wit