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frozen [14]
3 years ago
7

A rock is thrown straight up. What is the net external force acting on the rock when it is at the top of its trajectory (ignorin

g ar resistance)? a)There is none b)Gravity c)A normal force d)Thrust
Physics
1 answer:
Nat2105 [25]3 years ago
8 0

Answer:

b) Gravity

Explanation:

Gravity acts all of the time, when you apply force to a projectile it has to be more than the forces of the gravity and air resistance together so the projectile can move,  when the rock is at the top of its trajectory the force that you applied at the beginning is getting lost, so the other forces (air resistance and gravity) make the rock fall to the floor.

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Which statement is the correct representation of these electric field lines?
GuDViN [60]
I would say a. hope this helps
4 0
3 years ago
Read 2 more answers
A stone that is dropped freely from rest traveled half the total height in the last second. with what velocity will it strike th
alexira [117]

Answer:

hellooooo :) ur ans is 33.5 m/s

At time t, the displacement is h/2:

Δy = v₀ t + ½ at²

h/2 = 0 + ½ gt²

h = gt²

At time t+1, the displacement is h.

Δy = v₀ t + ½ at²

h = 0 + ½ g (t + 1)²

h = ½ g (t + 1)²

Set equal and solve for t:

gt² = ½ g (t + 1)²

2t² = (t + 1)²

2t² = t² + 2t + 1

t² − 2t = 1

t² − 2t + 1 = 2

(t − 1)² = 2

t − 1 = ±√2

t = 1 ± √2

Since t > 0, t = 1 + √2.  So t+1 = 2 + √2.

At that time, the speed is:

v = at + v₀

v = g (2 + √2) + 0

v = g (2 + √2)

If g = 9.8 m/s², v = 33.5 m/s.

4 0
3 years ago
A car is moving in uniform circular motion. If the cars speed were to double to keep the car moving with the same radius the acc
Stells [14]

Answer:

<em>The centripetal acceleration would increase by a factor of 4</em>

<em>Correct choice: B.</em>

Explanation:

<u>Circular Motion</u>

The circular motion is described when an object rotates about a fixed point called center. The distance from the object to the center is the radius. There are other magnitudes in the circular motion like the angular speed, tangent speed, and centripetal acceleration. The formulas are:

v_t=w\ r

\displaystyle a_c=\frac{v_t^2}{r}

If the speed is doubled and the radius is the same, then

\displaystyle a_c=\frac{(2v_t)^2}{r}

\displaystyle a_c=4\frac{v_t^2}{r}

The centripetal acceleration would increase by a factor of 4

Correct choice: B.

5 0
3 years ago
A roller coaster's velocity at the top of the hill is 10 m/s. Two seconds later it reaches the bottom of the hill with a velocit
svet-max [94.6K]

your answer is 8 m / sec²

5 0
2 years ago
A child on a bridge throws a rock straight down to the water below. The point where the child released the rock is 82 m above th
eimsori [14]

Answer:

40 m/s

Explanation:

given,

height of the fall, h = 82 m

time taken to fall, t = 1.3 s

rock velocity, v = ?

acceleration due to gravity, g = 9.8 m/s²

rock is released initial velocity, u = 0 m/s

using equation of motion

v² = u² + 2 a s

v² = 0 + 2 x 9.8 x 82

v² = 1607.2

v = 40 m/s

hence, rock's velocity is equal to 40 m/s

6 0
3 years ago
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