Question

Can some one pls give me the knowns and unknowns , formula and answer for question 4,5,6

Answer 1

4) The cart moves 5.0 m

5a) The force on the parachutist is 415.8 N (upward)

5b) The force on the parachutist will increase

6) The average force on the car is 5130 N (backward)

Explanation:

4)

First of all, we calculate the acceleration of the cart by using Newton's second law:

$F=ma$

where:

F = 14.0 N is the force exerted on the cart

m = 12.5 kg is the mass of the cart

a is its acceleration

Solving for a,

$a=\frac{F}{m}=\frac{14.0}{12.5}=1.12 m/s^2$

Now we can find the displacement of the cart by using the following suvat equation:

$s=ut+\frac{1}{2}at^2$

where:

s is the displacement

u = 0 is the initial velocity of the cart

$a=1.12 m/s^2$ is the acceleration

t = 3.00 s is the time

Substituting,

$s=0+\frac{1}{2}(1.12)(3.00)^2=5.0 m$

5a)

We start by calculating the acceleration of the parachutist, by using the following suvat equation

$v^2-u^2=2as$

where, choosing downward as positive direction:

v = 0 is the final velocity of the parachutist

u = 3.85 m/s is the initial velocity

a is the acceleration

s = 0.750 m is the vertical displacement

Solving for a,

$a=\frac{v^2-u^2}{2s}=\frac{0-(3.85)^2}{2(0.750)}=-9.9 m/s^2$

and the negative sign means the acceleration acts upward.

Now we can find the force exerted on the parachutist by using Newton's second law:

$F=ma$

where:

m = 42.0 kg is the mass

$a=-9.9 m/s^2$

Solving for F,

$F=(42.0)(-9.9)=-415.8 N$

And the negative sign means the force acts upward.

5b)

To answer this part, we just look again at the equation

$v^2-u^2=2as$

Which can be rewritten as

$a=\frac{v^2-u^2}{2s}$

We notice that if the parachutist comes to a rest over a short distance, the value of $s$ in the formula will decrease, so the acceleration of the parachutist will increase.

And now, by looking at the equation

$F=ma$

we notice that if the acceleration increases, the force exerted by the ground on the parachutist will increase as well.

6)

We start by calculating the acceleration of the car by using the equation

$a=\frac{v-u}{t}$

where

v = 9.50 m/s is the final velocity of the car

u = 16.0 m/s is the initial velocity

t = 1.20 s is the time taken for the velocity to change from u to v

Solving the equation,

$a=\frac{9.50-16.0}{1.20}=-5.4 m/s^2$

Now we can find the average force exerted on the car by using Newton's second law:

$F=ma$

where

m = 950 kg is the mass of the car

$a=-5.4 m/s^2$ is the acceleration

Substituting,

$F=(950)(-5.4)=-5130 N$

And the negative sign means the force acts in the opposite direction to the motion of the car.

Learn more about Newton's second law of motion and accelerated motion:

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