Chapter 7: Energy Question 1 2 pts Compare the kinetic energy of a 100.000 kg sh

Question

Chapter 7: Energy

Question 1 2 pts Compare the kinetic energy of a 100.000 kg ship moving at 98 km/h with that of an 87 9 kg astronaut in orbit moving at 25500 kmh. Your answer should be the decimal result of the ratio of the kinetic energy of the astronaut to the kinetic energy of the ship Question 2 2 pts A shopper pushes a grocery cart 24.4 m at constant speed on level ground, against a 18.7 N frictional force. He pushes in a direction 18.2 below the horizontal. What is the work done on the cart by friction? Question 3 2 pts Calculate the force needed to bring a 1032 kg car to rest from aspeed of 97 km/h in a distance of 117 m.

Explanation / Answer

From the given question,

Kinetic energy (KE)=(1/2)mv2

mass of ship(m1)=100,000 kg

velocity of ship(v1)=98 km/hr

mass of astraonaut(m2)=87.9 kg

velocity of astronaut(v2)=25500 km/hr

KE2/KE1= [(1/2)(m2)(v22)]/[(1/2)(m1)(v12)]

=(87.9)(25500)2/(100000)(98)2

=59.5

2.distance(x) =24.4 m

frictional force(Ff) =18.7 N

angle between direction of force and horizontal =18.2o

Work done on cart by friction=Ff x x

=18.7 x 24.4

=456.28 J

3. Initial speed(u) = 97 km/hr= 26.9 m/s

Final speed(v)=0

mass(m) = 1032 kg

distance(x)= 117 m

v2= u2 + 2as

02= 26.92 + 2(a)(117)

a=- 3.092 m/s2

Force= mass x acceleration

=1032 x 3.092

=3191 N

4. Gravitational potential energy= mgh

=9.4 x 109 x 9.8 x 75 J

=691 x 1010 Joules

5. work done by bird= mgh

=(75/1000) *9.8* 1.6

=1.176 J

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