# Problems on Physics

Topics: Friction, Mass, Force Pages: 3 (421 words) Published: November 14, 2014
﻿Chapter 5 pg 143
1. Mass 6.00 kg moved by 18.0N. What is its acceleration?
Divide both sides by m

a=18N/6.00kg convert N = 18N * 1kg*m/s^2 = 18kg*m/s^2
a=18kg*m/s^2/ 6.00 kg = 3m/s^2
a=3m/s^2
7. Truck pulls trailer with friction force of 870 N and a coefficient of friction 0.23. What is the trailer’s normal force.

870N=.023(FN) divide by .023
FN=870N/.023
FN=37826.7N
9. mass 13.0 kg dropped from a cliff. Find its weight

Fw=13.0kg * 9.8m/s^2
Fw=127.4kg*m/s^2
Fw=127.4N
13. A force of 175N needed to keep a 640N engine from sliding. What is the coefficient of static friction?

Ff=175N
FN=640N
divide by 640N
µ=175N/640N
µ=.273
15. find acceleration of a forklift mass 1400kg pushed by force 2100N opposed by frictional force of 425N.

Chapter 6 page 163
3. Box pushed with a force 125 N for 2.00 min. What is the impulse?

Impulse=125N*120s
Impulse=15000Ns=15000(kg*m/s^2)(s)
Impusle=15000kg*m/s
7. 15.0g bullet fired. Muzzle velocity 3250m/s from a rifle with mass 4.74kg and barrel length 75.0 cm.
A) How long is bullet in barrel? d/s=t
B) what is the force on the bullet while in the barrel?
C) Find the bullet’s momentum as it leaves barrel.
a) t=75cm/3250m/s 100cm=1m 75cm/1* 1m/100cm= .75m
t=.75m/3250m/s=2.307E-4s
time in barrel is 2.307E-4 seconds
b)

F=48750g*m/s/2.307X10-4s=48.750kg*m/s/2.307X10-4s
F=211313.394kg*m/s2 X 1N/1kg*m/s2=211313.394N
211,313.394N of force on the bullet as it leaves the barrel.
c) p=mv
p=15.0g * 3250m/s
p=48.75kg*m/s
9. Ball mass 575g traveling 3.50m/s collides with another ball mass 425g at rest. After collision, the lighter ball is traveling 4.03 m/s. what velocity is the velocity of the heavier ball after collision? m1=575gv1=3.50m/sv’1=?

m2=425gv2=0m/sv’2=4.03m/s
10. Railroad car mass 2.25X104kg traveling east 5.50m/s collides railroad car mass 3.00x104kg traveling west 1.50m/s. Find the velocity of the railroad cars that become coupled after...