Physics problems Mass/force check if correct?
by admin on Thursday, April 28th, 2011 | 3 Comments
1)A baseball is thrown by a pitcher from rest to 40m/s through a distance of .8m
a)find accereation on the ball
is it 2000/s^2?
2) A car of mass 1500kg can go from 20 m/s to 50 m/s in 4.5 seconds
a) find the accerleation of the car? 6.67m/s^2
b)how far did the car travel during that time? 135m
c)find the force used to accerlate the car?10005F
d) If this same car is hooked up to a trailer of 700kg, how much acceleration will the car now have? dont know
1.
a = ?
Vi = 0 m/s
Vf = 40 m/s
d = 0.8 m
Vf^2 = Vi^2 + 2ad
(40)^2 = (0)^2 + 2a(0.8)
a = 1000 m/s
2a. Correct
2b.
d = ?
Vf = 50 m/s
Vi = 20 m/s
a = 6.67m/s^2
Vf^2 = Vi^2 + 2ad
(50)^2 = 20^2 + 2(6.67)d
d = 157.42 m
2c. Correct except your answer should be in N (newtons)
2d. To answer this question you can use the net force on the car which you calculated in 2c.
Fnet = ma
(10005) = (700)a
a = 14.29 m/s^2
1) Use formula: vf^2 = vi^2 + 2 a d. We are told the ball starts from rest (vi = 0 m/s). Now we have: (40 m/)^2 = 2*a*(0.8 m). Solving for “a” we have the answer: a = 1000 m/s^2
2)
a) acceleration of the car = (change in velocity) / (time)
a = (50 m/s -20 m/s)/(4.5 s) = 6.67 m/s^2
b) use the formula from Problem #1 one more time:
(50 m/s)^2 = (20 m/s)^2 + 2(6.67 m/s^2)(d). Solving for d we have:
d = 157 m
c) the force accelerating the car is: F = ma = (1500 kg)(6.67 m/s^2) = 10,005 N
d) a = F/m = 10,005N)/(2200kg) = 4.55 m/s^2.
NOTE: It’s kind of strange you have two out of three answers wrong.
Good luck
1) follow this formula
(Velocity Final)^2-(Velocity Initial)^2=2(acceleration)(Distance)
(40m/s)^2-(0)^2=2(acceleration)(.8m)
Zero squared is zero. and 2x.8=1.6
(40m/s)^2=(acceleration)(1.6m)
40squared = 1600
(1600m^2/s^2)=(acceleration)(1.6m)
1600/1.6=1000….and the m^2/s^2/m -> m/s^2
Acceleration = 1000m/s^2*****************************
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2) a) [ ( V f ) - ( V i ) ] / Time = A
[50m/s-20m/s]/4.5s=A
A=6.67m/s^2 good work
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b) I got 157.5************************************************
same as the first
( V f ) ^ 2 – ( V f ) ^ 2 = 2 (A)(Distance?)
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c) Force = (mass)(acceleration)
F=(1500 kg)(6.67 m/s^2)
F=10,005 N**************************************
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d) Acceleration = Force/(Mass total)
A = (10,005N)/(2200kg)
A = 4.547 m/s^2**********************************