A child sits in a wagon with a pile of 0.64-kg rocks. If she can throw each rock with a speed of 7.5 m/s relative to the ground, causing the wagon to move, how many rocks must she throw per minute to maintain a constant average speed against a 3.9-N force of friction

Answer:

The number of rocks per minutes thrown is 49 rocks/min

Explanation:

Given;

mass of the rock, m = 0.64 kg

speed of the rock, v = 7.5 m/s

frictional force, $f_k$ = 3.9 N

For an object to move at a constant speed, the applied force must be equal to the frictional force.

$f_k = N(F_a)\\\\f_k = N(\frac{mv}{t})\\\\f_k = \frac{N}{t} (mv)\\\\\frac{N}{t} = \frac{f_k}{mv}$

where;

$F_a$ is the applied force

N/t is the number of rocks per minutes thrown

Substitute the given parameters;

$\frac{N}{t} = \frac{f_k}{mv}\\\\ \frac{N}{t} = \frac{3.9}{0.64*7.5}\\\\ \frac{N}{t} = 0.8125 \ \frac{rocks}{second} * \frac{60 \ seconds}{1 \ min} = 48.75 \ \frac{rocks}{min} \$

Approximately 49 rocks/min

5 0

3 years ago

55N of force are applied onto a table, but the force of friction is 8N. What is the net force acting on the table? Please explai

nirvana33 [79]

Answer:

get a tutor or something to help man

Explanation:

8 0

3 years ago

What is the acceleration of a car that goes from zero to 60m/s in 15s?

bonufazy [111]

Answer:What is the acceleration of a car that moves from rest to 15.0 m/s in 10.0 s? Vi=0, vf= 15.0 m/s,t=10.0s, a=? a= vf =vi/tA=15.0m/s-0m/s/10.0s = 15.0s/10.0s m/s*1/s =1.50 m/s^2 11.

Explanation:

3 0

3 years ago