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Classical Mechanics
1. Two identical cars, mass 1.0 tonnes, traveling at 30.0 kph in opposite directions, collide. During the collision, the front of each the cars crumples and becomes 15 cm shorter. So let's say that each car decelerates to rest over 15 cm. What is the magnitude of the average acceleration?
a) Magnitude of average acceleration: _____ m.s^−2. ( Careful with significant figures. )
b) What is the magnitude of the average external force that produces this acceleration?
Magnitude of average external force: _____ kN.
a) Magnitude of average acceleration: _____ m.s^−2. ( Careful with significant figures. )
b) What is the magnitude of the average external force that produces this acceleration?
Magnitude of average external force: _____ kN.
Classical Mechanics
1. In the car that decelerates from 30 kph to rest over 15 cm are two 70 kg passengers. One wears a seat belt and decelerates over 30 cm (with respect to the ground) (two significant figures). The other is not wearing a sea tbelt and decelerates over 5 cm* (with respect to the ground). What are the magnitudes of the average external forces acting on the two passengers during their de celerations? (Careful with significant figures: do both answers have the same precision?)
a) With a seat belt? _____ kN.
b) Without a seat belt? _____ kN.
a) With a seat belt? _____ kN.
b) Without a seat belt? _____ kN.
Classical Mechanics
1. A car has a drag coefficient Cd = 0.30, a frontal area of A = 1.9 m^2 and a mass 1.2 tonnes. It has a coefficient of rolling resistance,Cr, = 0.012. The rolling resistance is a force Fr = CrN, where N is the normal force.
i) What is Fr when traveling at v = 110 kph on a horizontal road? F= _____ N ,
Hint: Retain accurate values until the final calculation, but remember significant figures.
ii) Using the information from above:
What power (in kilowatts) is required to overcome Fr at this speed? P= _____ kW .
Hint: Retain accurate values until the final calculation, but remember significant figures.
i) What is Fr when traveling at v = 110 kph on a horizontal road? F= _____ N ,
Hint: Retain accurate values until the final calculation, but remember significant figures.
ii) Using the information from above:
What power (in kilowatts) is required to overcome Fr at this speed? P= _____ kW .
Hint: Retain accurate values until the final calculation, but remember significant figures.
Classical Mechanics
A car has a drag coefficient C_{d} = 0.30 Cd=0.30, a frontal area of A=1.9 m2 and a mass 1.2 tonnes. The density of air is 1.2 kg.m^{-3}
ii)What power (in kilowatts) is required to overcome the drag force at this speed?
P_{drag} = P drag= _____ kW.
A car has a drag coefficient C_{d} = 0.30 Cd=0.30, a frontal area of A=1.9 m2 and a mass 1.2 tonnes. It has a coefficient of rolling resistance, Cr, = 0.012. The rolling resistance is a force
Fr =CrN, where N is the normal force.
i) What is Fr when traveling at v=110 kph on a horizontal road? F= _____ N ,
Car physics, part 2.
Using the information from above:
ii) What power (in kilowatts) is required to overcome Fr at this speed? P= _____ kW .
ii)What power (in kilowatts) is required to overcome the drag force at this speed?
P_{drag} = P drag= _____ kW.
A car has a drag coefficient C_{d} = 0.30 Cd=0.30, a frontal area of A=1.9 m2 and a mass 1.2 tonnes. It has a coefficient of rolling resistance, Cr, = 0.012. The rolling resistance is a force
Fr =CrN, where N is the normal force.
i) What is Fr when traveling at v=110 kph on a horizontal road? F= _____ N ,
Car physics, part 2.
Using the information from above:
ii) What power (in kilowatts) is required to overcome Fr at this speed? P= _____ kW .
Classical Mechanics
I drag a mass m=21 kg in a straight line, along a horizontal surface, a distance D=23 m . I drag it at constant speed v=0.90 m.s−1 in a straight line using a horizontal force. The coefficients of friction are \mu_{s} = 1.2μ
s
=1.2 and \mu_{k} = 1.1μ
k
=1.1. How much work do I do?
s
=1.2 and \mu_{k} = 1.1μ
k
=1.1. How much work do I do?
Classical Mechanics
A plank of length 2.89 m is to be balanced on a see-saw. On one side of the plank hangs a mass 1 =6.32 kg, and on the other side of the plank there is a massless, frictionless pulley. This pulley has a mass 2 =22.2 kg on one side and a mass 3 =6.25 kg on the other side. What is the distance from the see-saw's pivot to the point where mass 1 must hang in order for this plank to be stationary after being released from rest?
Classical Mechanics
A black of mass 4.0 kg starts from rest and slides down a surface which corresponds to a quarter of a circle of 2.0 m radius.1)if the curved surface is smooth, find the speed at the bottom.2)if the speed at the bottom is 2.0m/s, calculate the energy dissipated due to friction in the descent.3)after the block reaches the horizontal with a speed of 2.0m/s it slides to a stop in a distance of 1.5m . Calculate the frictional force acting on the horizontal surface. Take g=10m/s2.
Classical Mechanics
You and your friend find yourselves in an unfortunate situation. A shopping-cart-related stunt has gone wrong and now your friend is stuck in a shopping cart and is on a crash course for your house with speed V= 1.78 m/s. You are on the roof of your house, which forms an angle θ=40.9 with the horizontal, and it's your job to stop your friend. You size up the situation and see that the mass of your friend and the cart combined is M=42.0 kg and luckily you have some camera equipment with you whose total mass is m=40.3 kg. Your plan is as follows. You're going to climb up the roof, place the equipment on the (frictionless) rooftoop, and let it slide off the roof, which is a height h=3.60 m above the ground. Your friend is going to catch the equipment and get slowed down by it. How far up the roof do you need to climb in order for your friend to come a complete stop?
Classical Mechanics
1. Two identical cars, mass 1.0 tonnes, traveling at 30.0 kph in opposite directions, collide. During the collision, the front of each the cars crumples and becomes 15 cm shorter. So let's say that each car decelerates to rest over 15 cm. What is the magnitude of the average acceleration?
a) Magnitude of average acceleration?
b) Magnitude of average external force?
2. In the car that decelerates from 30 kph to rest over 15 cm are two 70 kg passengers. One wears a seat belt and decelerates over 30 cm (with respect to the ground) (two significant figures). The other is not wearing a seat belt and decelerates over 5 cm* (with respect to the ground). What are the magnitudes of the average external forces acting on the two passengers during their decelerations? (Careful with significant figures: do both answers have the same precision?)
a) With a seat belt? _____ kN
b) Without a seat belt? _____ kN
a) Magnitude of average acceleration?
b) Magnitude of average external force?
2. In the car that decelerates from 30 kph to rest over 15 cm are two 70 kg passengers. One wears a seat belt and decelerates over 30 cm (with respect to the ground) (two significant figures). The other is not wearing a seat belt and decelerates over 5 cm* (with respect to the ground). What are the magnitudes of the average external forces acting on the two passengers during their decelerations? (Careful with significant figures: do both answers have the same precision?)
a) With a seat belt? _____ kN
b) Without a seat belt? _____ kN
Classical Mechanics
1. A mass breaks suddenly into two parts, masses M and m, with speeds V and v respectively and carrying a total kinetic energy K. If M / m = R =, what fractions of K does each of the masses carry? (Think about significant figures.)
a) M carries _____ K.
b) m carries _____ K.
2. A machine gun fires bullets, each with mass m = 55 g at a speed of u = 450 m.s^-1. The gun fires 5.0 bullets per second. Let's use it as a rocket engine. What thrust does it produce?
3. Let's combine momentum and collisions with some of the other things we've learned. A small block of mass M = 0.201 kg hangs on the end of a light, in extensible string, length R = 25 cm. A small dart (of mass m=0.10 kg) traveling in the horizontal direction collides with and remains fixed in the block. What is the minimum speed v of the dart such that the combined object completes a circular path around the support point of the block? How fast must the block be traveling at the top?
a) M carries _____ K.
b) m carries _____ K.
2. A machine gun fires bullets, each with mass m = 55 g at a speed of u = 450 m.s^-1. The gun fires 5.0 bullets per second. Let's use it as a rocket engine. What thrust does it produce?
3. Let's combine momentum and collisions with some of the other things we've learned. A small block of mass M = 0.201 kg hangs on the end of a light, in extensible string, length R = 25 cm. A small dart (of mass m=0.10 kg) traveling in the horizontal direction collides with and remains fixed in the block. What is the minimum speed v of the dart such that the combined object completes a circular path around the support point of the block? How fast must the block be traveling at the top?
