A bullet is fired with a certain velocity at an angle theta above the horizontal

Question

A bullet is fired with a certain velocity at an angle theta above the horizontal at a location where g = 10.0 m/s^2. The initial x- and y-components of its velocity are 86.6 m/s and 50.0 m/s respectively. What is the initial speed of the bullet? 50.0 m/s 100 m/s 136 m/s 36.6 m/s 86.6 m/s ________________ A ball is thrown horizontally with an initial velocity of 40 m/s from a height of 10 m. How long will it take for the ball to touch the ground ? Use g = 10 m/s^2. 0.70 second 1.4 second 1.0 second 2.4 seconds 2.0 seconds ______________ What average net force is required to accelerate a car with a mass of 1200 kg from 0 to 27.0 m/s in 10.0 ? 1, 800 N 3, 240 N 4360 N 444 N 1620 N _____________ A packing crate slides down an inclined ramp at constant velocity. Thus, we can deduce that a net upward force is acting on it. It is not acted on by appreciable gravitational force. a net downward force is acting on it. A frictional force is acting on it. it is not acted on by appreciable normal force. _______________

Explanation / Answer

(14) initial speed of the bullet

v = sqrt[vx^2 + vy^2]

v = sqrt[86.6^2 + 50.0^2]

v = 99.99 m/s = 100 m/s

(15) Given that

initial velocity u = 40 m/s

height h = 10 m

find the time taken to reach the ground

time t = sqrt[2*h/g]

= sqrt[2*10/10]

= 1.4 sec

(16) Force F = m*a

so need to find the acceleration

acceleration = change in velocity/time

accel = (27 m/s - 0)/10 s

= 2.7m/s^2

F = 1200 kg * 2.7 m/s^2

Fnet = 3240 N

(17) frictional force is acting on it

Explanation :

There are three forces acting on the body :

(1) gravitational force vertically down

(2) normal force from the incline perpendicular to the incline

(3) friction force up the incline

As the crate slides down with constant velocity, the net force on it is 0.

So, net force due to all the 3 forces is 0

NOTE : the frictional force up the incline is cancelled by the component of force of gravity down the incline

The normal force cancels out the other component of the force of gravity.

Thus the net effect is 0 force.

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.