SOLUTION: 1. If you take a car moving at constant velocity of 40 km/hr towards east for three hours them turn right towards north and continues traveling at same speed for two hours and sudd
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Question 662387: 1. If you take a car moving at constant velocity of 40 km/hr towards east for three hours them turn right towards north and continues traveling at same speed for two hours and suddenly stops. At this moment, how far are you from your point of origin?
2. A 200 ladder is leaning against 25 ft. vertical wall. If the foot of the ladder makes a 75 degree angle with horizontal ground, how far are the tips of the ladder from the top edge of the wall?
3. A boy standing in front of a cliff claps his hands ad 2.50 seconds later he hears an echo. How far away is the cliff if sounds travel at 343 m/sec?
4. A motorbike has an initial velocity of 20 m and accelerates at -1.0m/sec?
4a Finds its velocity after 10 seconds
4b What its displacement after 10 seconds
4c give its velocity after 30 seconds
5. A 10 kg block of wood is at rest on a level concrete floor?
5a What will happen if horizontal force of 50N is applied to the block?
5b What is the minimum horizontal force needed to keep to start the block moving if coefficient of static friction is = 0.5
5C What is the minimum horizontal force needed to keep the block in motion at constant speed if coefficient of kinetic friction is =0.4?
6. A 70 kg man is fired from a compressed air canon and emerged from the 20 m barrel at 40 m/second, Using Newton's Second Law, find the average force o him durig the firing of the cannon.(start by finding the acceleration with the Formula V1 =V2o +2 ax and then F=ma
7. Compare the potential energy of a 1,500 kg car of the top at a hill 50 m high with its kinetic energy when moving at 100 km/hr?
8.A 4.5 kg rifle fires a 10 g bullet with a velocity of 1000 m/sec. What is the recoil velocity of the riffle?
Answer by KMST(5328) (Show Source): You can put this solution on YOUR website!
1. The distance (in km) traveled by a car moving at constant 40 km/hr for 3 hours is
.
The distance (in km) traveled by a car moving at constant 40 km/hr for 2 hours is
.
If the car was traveling km east for the first 3 hours,
and then traveled km north for the next 2 hours,
we can represent the trip like this:
The distance, from start to end, in km, is =about km.
2. A ft ladder, leaning against ft vertical wall, making a angle with horizontal ground, can be represented as
In ft, = about (rounding)
How far are the tips of the ladder from the top edge of the wall?
In feet, . I would say 5 ft 8 inches.
3. A boy standing in front of a cliff claps his hands, and 2.50 seconds later he hears an echo. How far away is the cliff if sounds travel at 343 m/sec?
The sound traveled a distance to the cliff and a distance back to the boy
in at /
--> --> (rounded to 3 significant figures)
4. A motorbike has an initial velocity of / and accelerates at -1.0/.
NOTE: I entered reasonable units, and assume the acceleration is really negative; the motorcycle is slowing down).
4a Finds its velocity after 10 seconds
--> /
4b What its displacement after 10 seconds
We could multiply / over those 10 seconds, to get
We could use --> --> --> -->
It is 150 m further ahead in the direction it was originally moving.
4c give its velocity after 30 seconds
Very funny!
If the motorcycle keeps accelerating at -1.0/, it will stop after 20 seconds and will start moving in the opposite direction at increasing speed.
I hope the bike rider just made a U-turn, and is not riding backwards,
In that case, the final velocity will be m/s.
That is in one hour, .
5. A 10 kg block of wood is at rest on a level concrete floor.
Taking the acceleration of gravity as /,
the normal (perpendicular) force pressing the block to the concrete (the block's weight) is .
5a What will happen if horizontal force of 50N is applied to the block?
I would have thought nothing, because the static friction coefficient between wood and concrete is often quoted as 0.62, but part b suggest that your concrete is more slippery than that. Maybe it is, and the block will start moving.
5b What is the minimum horizontal force needed to start the block moving if coefficient of static friction is = 0.5?
That would be
5C What is the minimum horizontal force needed to keep the block in motion at constant speed if coefficient of kinetic friction is =0.4?
That would be .
I'd answer because all the given data had just 1 or 2 significant digits.
6. A 70 kg man is fired from a compressed air canon and emerged from the 20 m barrel at 40 m/s, Using Newton's Second Law, find the average force on him during the firing of the cannon.(Start by finding the acceleration with the Formula and then ).
The final velocity, on exiting the barrel is m/s.
The initial velocity, before being accelerated, is m/s, of course.
The distance covered while accelerating is the length of the barrel, so m.
Substituting in the formula above,
--> --> /
Then , with kg, results in
N --> N
7. Compare the potential energy of a 1,500 kg car of the top at a hill 50 m high with its kinetic energy when moving at 100 km/hr?
Using /, and we calculate the potential energy of the car at the top the hill as
--> --> J.
The kinetic energy can be calculated as ,
and with and , m/s,
so for the 1500 kg car moving at 100 km/hr
--> --> J.
The potential energy was greater tan the kinetic energy.
If the potential energy could efficiently convert to kinetic energy, the car would have more than enough energy to reach 100 km/hr by just rolling down the hill.
8.A 4.5 kg rifle fires a 10 g bullet with a velocity of 1000 m/sec. What is the recoil velocity of the riffle?
The mass of the 10 g bullet, in kg is 0.010 kg.
Conservation of momentum requires that the momentum (mass times velocity) of the riffle must be the same in magnitude (but with opposite direction) as the momentum of the bullet, so the recoil velocity, , in m/s satsifies the equation
--> --> --> m/s (rounded).
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