Physics Questions O Level- Dynamics (Newton's Laws)

[shariq123]

Hello, I am new to these forums.
I was seeking someone who could kindly answer a few question of mines.
They are as follows and are related to the Chapter of Dynamics:
P.S. Please show the working and clarification of concepts

1. A car of 500 kg moves along a level road with an acceleration of 2 ms/s^2.
If its engine is exerting a forward force of 1100 N, what resistance is the car experiencing?

2. Find the constant force necessary to accelerate a car of mass 600 kg from rest to 25 m/s in 12s if the resistance to motion is
a) zero b )350n

3. A train of mass 60 tonnes is travelling at 40 m/s when the brakes are applied.
If the resultant braking force if 40 kN find the distance the train travels before coming to rest.

4. Find the constant force necessary to accelerate a car of mass 1000kg from 15 m/s to 20 m/s in 10 s against resistances totalling 270N.

5. A van of mass 2 tonnes moves along a level road against resistances of 700n.
If its engine is exerting a forward force of 2200N, find the acceleration of the van.


Thanks once again.
Regards,
Shariq

 

[Gémeaux]

F=?
m=500
a=2
Newton's 2nd law: F=ma
F=500*2=1000N
force exerted=1100N
1100-1000= 100N(extra exertion) hence is the resistance
correct me if im wrong bt i *thnk* dat'd b how its solved

 

[Gémeaux]

2.
F=?
m=600
u=0
v=25
t=12
find acc. a=(v-u)/t
(25-0)/12 = 2.0833m/s^2

now F=ma
F= 600*2.0833= 1249.998 => 1250N

 

[Gémeaux]

for above^^^ i didnt see.
now if R=0 then F=1250
but if R=350, add it to F, F(2)= 1250+350=1600N

 

[shariq123]

Thanks for the answers, but why do you add 350 to 1250 instead of subtracting it?
That part has been confusing me

 

[Gémeaux]

4. acc (a)= (20-15)/10= 0.2m/s^2
F=ma, =1000*0.2= 200 N
but due to resistances F will be 200+270= 470N

xtremely sory if u ever find dat these solutions r wrong =P

 

[Gémeaux]

i thnk we'd add em cuz we have to overcome it... equal n *opposite* force is to b applied to cancel it out. so opposite to resistance wud be the one frm engine i guess

 

[shariq123]

for 4 the answer in the answer key is 770 N but Idk how to get that
And oh ok i think I kinda get why you added them

 

[Gémeaux]

sooooo soryy.. ma bad.. acc ws 0.5 i by mistake took it 0.2..
now F= 500N
then add 270N into it u get 770N