PHYSICS SET UP

Ray Williams

April 11, 2013

Module 2 - Case

Newton's Laws

1. State and explain Newton's Three Laws of motion, giving examples from daily life.

Answer: Law I). Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it.

EX. If a sled is going down a hill it will stay in motion until it hits the end of the hill or the pavement and then it stops

Law II)The relationship between an object's mass m, its acceleration a, and the applied force F is F = ma. Acceleration and force are vectors (as indicated by their symbols being displayed in slant bold font); in this law the direction of the force vector is the same as the direction of the acceleration vector.

EX. Is the amount of force we put on the bowling ball and the mass of the bowling ball determines its acceleration.

Law III)For every action there is an equal and opposite reaction.

EX. Is when we exercise and do pushups on the floor.

2. A 1500 kg car is accelerating at a constant rate. In two seconds, its velocity goes from 10

to 30 km/hr. What is the total force acting on the car, in N?

Answer: acceleration=(30-10)*10^3/(3600*2)=25/9 m/s^2

F=ma=1500*25/9=4166.7 N.

the total force on the car is around 4166.7 N.

3. An astronaut in his space suit has a total mass of 300 kg. His weight on the asteroid Ceres is 2.00 N. What is the acceleration of gravity on Erewhon?

Answer: a=F/m=2/300=6.67*10^(-3) m/s^2

therefore, the accelerate on of gravity on Erewhon is around 6.67*10^(-3) m/s^2

4. A 50 kg cannon shell is subjected to a constant acceleration of 1200 g while in the cannon barrel. What force is the burning propellant exerting on the shell?

Answer: F=ma=50*1200g=60000g N.

The force is around 60000g N.

5. Four forces, represented by four vectors, are plotted in standard position on the Cartesian plane. The lengths of the vectors, in arbitrary units, represent the strength of the forces in N. The forces are being applied to an object with a mass of 1 kg, located at the origin. In what direction will the object accelerate, and how rapidly? The force vectors are A(5,5) B(-3,-2) C(-1, 6) and D(-6, 3).

Answer: Fx=5-3-1-6=-5, Fy=5-2+6+3=12.

F=sqrt(5^2+12^2)=13 N..

acceleration=F/m=13/1=13 m/s^2

direction=arccos(-5/13)=112.62 degree.

the acceleration is 13 m/s^2 and the direction is 112.62 degree