Who can help with Physics force problems?

Question

hello I have a few questions
thankyou!

1) Calculate the force you exert as you stand on the floor assuming you weigh 180 lb. (1 lb = 0.454 kg).

2)A dragster starts with zero velocity and completes a 402.1 m (0.2513 mile) run in 4.910 s. If the car had a constant acceleration, what would be its acceleration and final velocity?
m/s2 =?
m/s=?

3)After a day of testing race cars, you decide to take your own 1460 kg car onto the test track. While moving down the track at 10.0 m/s, you uniformly accelerate to 32.0 m/s in 10 s. What is the average net force that you have applied to the car during the 10 s interval?
N=?
n is newtons

4)A race car has a mass of 718 kg. It starts from rest and travels 44.0 m in 3.0 s. The car is uniformly accelerated during the entire time. What net force is exerted on it?
N=?

5)Your mass is 80 kg. You stand on a bathroom scale in an elevator on Earth.

(a) What force would the scale exert when the elevator moves up at a constant speed?
N=?
(b) What force would the scale exert when it slows at 2.2 m/s2 while moving upward?
N=?
(c) What force would the scale exert when it speeds up at 2.2 m/s2 wile moving downward?
N=?
(d) What force would the scale exert when it moves downward at a constant speed?
N=?
(e) What force would the scale exert when it slows to a stop at a constant magnitude of acceleration?



6) A boy exerts a 38 N horizontal force as he pulls a 54 N sled across a cement sidewalk at constant speed. What is the coefficient of kinetic friction between the sidewalk and the metal sled runners? Ignore air resistance.



thankyou for the help everyone!

Answer 1

1) 180 lbs downward. The floor pushes back upwards with 180 lbs. (Pounds are force units)
2) s = 0.5*a*t^2 (s=dist., a=acceleration, t=time)
402.1 = 0.5 * a * 4.91^2
a = 33.36 m/(s^2)
3) F = ma and v = v0 + at
v=speed, v0 = initial speed, F=force, m=mass
a = (32-10)/10 = 2.2 m/(s^2)
F = ma = 1460*2.2 = 3212 Newtons
4) find a using s=0.5*a*t^2
then find F=ma
5) gravity = 9.8 m/(s^2)
a) no change (no acceleration added to gravity)
b) relative gravity in elevator = (9.8-2.2) = 7.6
which is 0.7755 of normal gravity.
Therefore scale should show 77.55% of your "normal" weight.
c) same as b
d) normal weight
e) insufficient data
6) The friction is 38 N, therefore the coefficient is 38/54.

Answer 2

1) First convert 180lb into kilograms: (180lb)(0.454kg/lb) = 81.72kg.
Then using weight = (mass)(gravity), weight = (81.72)(9.8) = 800.856 N

2) Using the following kinematic equation: disance = (v-initial)(t) + 0.5(a)(t-squared) and plugging in the given information of a distance of 402.1m, time of 4.910s, and initial velocity of 0m/s solving the equation for 'a' yields 33.358 m/s2

For the second part use the calculated acceleration and plug it and the other info into v-final = v-initial + at and you get a final velocity of 163.788 m/s

3) Take the given information of v-initial = 10m/s, v-final = 32m/s, and t = 10s and plug it into v-final = v-initial + at and solve for 'a'. This gets an acceleration of 2.2 m/s2. Plug this acceleration and the mass of the car into F=ma and you get 3212 N

Hope this helps. I am at work so I don't have time to solve the others. :-)

Answer 3

These are not hard problems. Read your text. Try to do these problems. If you are stuck on a specific concept, I will be glad to help.