Sorry if it is alot of questions
1. A crate falls from an airplane flying horizontally at an altitude of 2000 m. Neglecting air resistance, about
how long will the crate take to strike the ground?
a. 10 seconds
b. 20 seconds
c. 400 seconds
d. 100 seconds
2. An object is dropped and falls freely to the ground with an acceleration of 1 g. If it is thrown upward at an
angle instead, its acceleration would be __________.
a. 0 g.
b. 1 g downward.
c. 1 g upward.
d. larger than 1 g.
e. none of the above
3. A projectile is thrown upward and moves in a parabolic path. At what point along this path are the velocity
and acceleration vectors for the projectile perpendicular to each other?
a. Nowhere
b. At the highest point
c. At the launch point
d. Unable to determine
4. Which best approximates the resultant of a pair of 10-unit vectors at right angles to each other?
a. 0 N.
b. 10 N.
c. 14 N.
d. 20 N.
5. When the angle of an incline with a block resting on it increases, the normal support force __________.
a. increases.
b. stays the same.
c. decreases.
6. If a horse pulls on a wagon at rest, the wagon pulls back equally as much on the horse. Will the wagon be set
into motion?
a. No, because the forces cancel each other.
b. Yes, because there is a net force acting on the wagon.
c. Yes, because there is a time delay between action and reaction.
d. Yes - The horse's pull on the wagon is larger than the wagon's pull on the horse.
7. An object following a straight-line path at constant speed __________.
a. has a net force acting on it in the direction of motion.
b. has zero acceleration.
c. must be moving in a vacuum.
d. has no forces acting on it.
e. none of the above
Answers:
1.b
2.c
3.b
4.b
5.b
6.a
7.b
1. b right
2. AhhhgggHHH a is 1 g downward the whole time whatever is airborne
3. b right
4. sqrt(10^2+10^2) =10sqrt2 = 14 c
5. c! when you reach steep enough it goes to zero
6. B ! the forces are ALWAYS equal and opposite (Law 3) however unless the friction on the ground or in wheels is included, the cart accelerates.
7. b yes
Thank You Sir
1. To determine the time it takes for the crate to strike the ground, we can use the equation of motion:
s = ut + 1/2at^2
Where s is the vertical displacement (2000 m), u is the initial velocity (0 m/s), a is the acceleration due to gravity (-9.8 m/s^2), and t is the time we are solving for.
Plugging in the values, we get:
2000 = 0*t + 1/2*(-9.8)*t^2
Simplifying the equation, we get:
-4.9t^2 = -2000
Dividing both sides by -4.9, we get:
t^2 = 408.16
Taking the square root of both sides, we get:
t ≈ 20.2 seconds
Therefore, the crate will take approximately 20 seconds to strike the ground. So the correct answer is b.
2. When an object is dropped and falls freely to the ground, its acceleration is equal to the acceleration due to gravity (9.8 m/s^2) in the downward direction. If it is thrown upward at an angle instead, its acceleration would still be equal to the acceleration due to gravity, but in the opposite direction (upward). Therefore, the correct answer is c - 1 g upward.
3. The velocity and acceleration vectors for a projectile are perpendicular to each other at two points along its path - the highest point and the launch point. At the highest point, the projectile momentarily comes to a stop and changes direction, so the velocity and acceleration vectors are perpendicular. Therefore, the correct answer is b - at the highest point.
4. When two vectors are at right angles to each other, the magnitude of their resultant can be found using the Pythagorean theorem. In this case, both vectors have a magnitude of 10 units, so the resultant magnitude can be calculated as:
Resultant magnitude = sqrt(10^2 + 10^2) = sqrt(200)
Approximately, sqrt(200) ≈ 14.14
Therefore, the correct answer is c - 14 N.
5. When the angle of an incline with a block resting on it increases, the normal support force exerted by the incline on the block decreases. The normal force is the force exerted perpendicular to the surface of the incline to support the weight of the block. As the incline becomes steeper, the component of the weight force acting perpendicular to the surface decreases, resulting in a decrease in the normal support force. Therefore, the correct answer is c - decreases.
6. According to Newton's Third Law of Motion, for every action, there is an equal and opposite reaction. When the horse pulls on the wagon, the wagon exerts an equal and opposite force on the horse. However, the forces cancel each other out and do not result in a net external force on the wagon. Therefore, the wagon will not be set into motion. The correct answer is a - No, because the forces cancel each other.
7. An object following a straight-line path at constant speed has zero acceleration. This is because acceleration is the rate of change of velocity, and if the speed is constant, there is no change in velocity. Therefore, the correct answer is b - has zero acceleration.
1. To solve this problem, we can use the kinematic equation for vertical motion:
s = ut + (1/2)gt^2
where s is the displacement (2000m in this case), u is the initial velocity (0m/s since the crate is dropped), g is acceleration due to gravity (-9.8m/s^2), and t is the time we're trying to find.
Plugging in the values, we get:
2000 = 0*t + (1/2)*(-9.8)*t^2
Simplifying the equation:
2000 = -4.9t^2
Dividing both sides by -4.9:
-2000/4.9 = t^2
Taking the square root of both sides:
t ≈ +- 19.37 seconds
Since time cannot be negative in this context, we ignore the negative value. Therefore, the time it takes for the crate to strike the ground is approximately 19.37 seconds.
None of the given options match the calculated value exactly, but the closest one is option b, 20 seconds.
2. When an object is dropped, its acceleration is equal to the acceleration due to gravity, which is approximately 9.8 m/s^2. If it is thrown upward at an angle, its acceleration would still be the same as gravity is always acting downward regardless of the object's initial velocity or angle. Therefore, the answer is option b, 1 g downward.
3. When a projectile is thrown upward and moves in a parabolic path, the velocity and acceleration vectors are never exactly perpendicular to each other. The projectile is always accelerating downward due to the force of gravity. Therefore, the answer is option a, nowhere.
4. When two vectors are at right angles to each other, their resultant magnitude can be calculated using the Pythagorean theorem. The magnitude of the resultant vector is given by the square root of the sum of the squares of the individual vector magnitudes. In this case, both vectors have a magnitude of 10 units. Using the Pythagorean theorem, we can calculate the magnitude of the resultant vector:
Resultant magnitude = sqrt((10^2) + (10^2))
= sqrt(200)
≈ 14.14 units
Therefore, the answer is option c, 14 N.
5. The normal support force is the force exerted by a surface to support the weight of an object resting on it. When the angle of an incline with a block resting on it increases, the component of the weight perpendicular to the incline decreases. As a result, the normal support force also decreases. Therefore, the answer is option c, decreases.
6. According to Newton's third law of motion, for every action, there is an equal and opposite reaction. When the horse pulls on the wagon, the wagon exerts an equal and opposite force on the horse. These forces cancel each other out, resulting in a net force of zero on the wagon. As a result, the wagon will not be set into motion. Therefore, the answer is option a, No, because the forces cancel each other.
7. An object following a straight-line path at constant speed has zero acceleration. This means that there is no net force acting on the object. Therefore, the answer is option b, has zero acceleration.